Erectile Dysfunction Glossary: Medical Terms, Causes, Tests and Treatments Explained

• 10 November 2026
• Mr. Leon Almashan

Last updated on November 10, 2026

Erectile dysfunction is far more common than most men realise. The British Association of Urological Surgeons puts it at between 50% and 55% of men aged 40 to 70, and in the landmark Massachusetts Male Aging Study state that the likelihood of some degree of ED rose from 39% at age 40 to 67% at age70.

Yet many men only start reading about the condition once it affects them, and the language can be confusing often a mixture of Latin and anatomical names that they have never heard of.

To make this easier, at MansMatters we have compiled a plain-English glossary covering the terms you are most likely to come across when researching erectile dysfunction. This glossary is organised across nine sections: the conditions and how they are diagnosed, the health conditions and risk factors linked to ED, the anatomy of the penis, how an erection works, blood flow and vascular health, hormones and testosterone, the questionnaires clinicians use, the tests and investigations, and the treatments and technology available.

It is written for anyone who needs to understand the language of erectile dysfunction: men looking into treatment for themselves, partners trying to make sense of a diagnosis, medical and nursing students, GPs and practice nurses who see ED in clinic, and journalists or researchers who want accurate definitions. Each entry begins with a simple explanation, so you can build your understanding from the basics. Once you are familiar with the fundamentals, the same terms give you the vocabulary to read clinical guidelines, research papers and your own test results with confidence, and to have a more informed conversation with your GP or Mem’s health specialist.

Erectile Dysfunction: Conditions and Diagnosis

Erectile Dysfunction (ED): Erectile Dysfunction (ED) is the persistent inability to achieve or maintain an erection firm enough for satisfactory sexual activity. It is one of the most common sexual health conditions in men, affecting around half of men aged 40 to 70 to some degree (BAUS), and can be a physical, psychological or combined problem.

Impotence: Impotence is an older clinical term for erectile dysfunction, used less frequently in modern medical practice.

Erectile Disorder: Erectile Disorder is the formal diagnostic name for erectile dysfunction used in psychiatric and sexual medicine classifications, applied when erection difficulties have lasted at least six months and cause the man significant distress.

Organic Erectile Dysfunction: Organic Erectile Dysfunction is ED caused by an underlying physical factor, such as reduced blood flow, nerve damage, or hormonal imbalance, rather than psychological causes.

Psychogenic Erectile Dysfunction: Psychogenic Erectile Dysfunction is ED caused primarily by psychological factors such as anxiety, stress, or relationship difficulties, occurring even without an underlying physical cause.

Mixed Erectile Dysfunction: Mixed Erectile Dysfunction is ED with both a physical and a psychological component, and is the most common pattern seen in clinic. A small physical change, such as reduced blood flow, often leads to worry about performance, which then makes the erection problem worse.

Vasculogenic Erectile Dysfunction: Vasculogenic Erectile Dysfunction is the most common physical cause of ED, occurring when the blood vessels supplying or draining the penis fail to function properly.

Arterial Erectile Dysfunction: Arterial Erectile Dysfunction, also called arteriogenic ED, is ED caused by too little blood reaching the penis because the arteries that supply it have narrowed or hardened. The penile arteries are among the smallest in the body, so this form of ED can appear years before heart disease is diagnosed.

Venogenic Erectile Dysfunction: Venogenic Erectile Dysfunction is ED in which blood enters the penis normally but is not held there because the veins that should close during an erection fail to seal. The result is an erection that is reached but cannot be kept.

Neurogenic Erectile Dysfunction: Neurogenic Erectile Dysfunction is ED caused by damage to the nerves that carry the signal for an erection from the brain and spinal cord to the penis. Diabetes, multiple sclerosis, spinal cord injury and pelvic or prostate surgery are the usual causes.

Hormonal Erectile Dysfunction: Hormonal Erectile Dysfunction is ED that develops when the hormones controlling sexual function are out of balance, most often because testosterone is low, prolactin is raised or the thyroid is under- or overactive. It usually comes with a fall in sex drive as well as weaker erections.

Drug-Induced Erectile Dysfunction: Drug-Induced Erectile Dysfunction is ED caused as a side effect of a medicine or recreational drug rather than by an underlying illness. Blood pressure tablets, antidepressants, antipsychotics, some prostate medicines, alcohol and illicit drugs are the most frequent culprits, and erections often recover when the drug is changed or stopped under medical advice.

Post-Prostatectomy Erectile Dysfunction: Post-Prostatectomy Erectile Dysfunction is ED that develops following prostate removal surgery, usually due to disruption of the nerves and blood vessels responsible for erections.

Situational Erectile Dysfunction: Situational Erectile Dysfunction is ED that occurs only in particular circumstances, such as with a new partner or under pressure, while erections during sleep, on waking or alone are normal. Because the erectile mechanism is working, the cause is almost always psychological.

Primary Erectile Dysfunction: Primary Erectile Dysfunction is lifelong ED in a man who has never been able to achieve or sustain an erection adequate for intercourse. It is uncommon, and because it often has a structural, vascular or neurological cause it should be assessed by a specialist.

Secondary Erectile Dysfunction: Secondary Erectile Dysfunction is ED that develops in a man who previously had normal erections. It is by far the most common form and usually reflects a change in health, medication or circumstances, such as cardiovascular disease, diabetes, hormonal change or stress.

Mild Erectile Dysfunction: Mild Erectile Dysfunction is the early stage of ED, in which erections are still achievable but are less firm, less reliable or harder to keep than before. On the IIEF-5 questionnaire it corresponds to a score of 17 to 21 (Rosen et al., 1999), and it is often the first sign of a vascular or lifestyle problem that is worth investigating.

Moderate Erectile Dysfunction: Moderate Erectile Dysfunction is ED in which erections are frequently not firm enough, or do not last long enough, for satisfactory intercourse, and tablets may give a reduced or inconsistent response. It corresponds to an IIEF-5 score of 8 to 11.

Severe Erectile Dysfunction: Severe Erectile Dysfunction is ED in which penetrative sex is difficult or impossible and oral medication has little or no effect. It corresponds to an IIEF-5 score of 5 to 7 and is usually linked to a significant physical cause such as advanced vascular disease, long-standing diabetes or nerve damage after surgery.

Complete Erectile Dysfunction: Complete Erectile Dysfunction is the total and persistent absence of erections firm enough for any sexual activity, including the loss of the involuntary erections that normally occur during sleep. It is the end point of the ED severity scale and almost always has a physical cause.

Performance Anxiety: Performance Anxiety is worry about being able to get or keep an erection, or to satisfy a partner, which itself prevents the erection from happening. The anxiety activates the body’s stress response, and the adrenaline released works directly against the relaxed state needed for blood to flow into the penis, so each failure feeds the next.

Porn-Induced Erectile Dysfunction (PIED): Porn-Induced Erectile Dysfunction (PIED) is a term for ED in which a man can achieve erections to pornography but struggles with a partner, usually after heavy or long-term pornography use. It is not a formal medical diagnosis, but it is increasingly reported in men under 40 with no physical cause and generally improves when pornography use is reduced.

Hard Flaccid Syndrome: Hard Flaccid Syndrome is an uncommon condition in which the penis stays firm, retracted and rubbery when it should be soft, often with pain in the penis or perineum and weaker erections. It is thought to involve overactive pelvic floor muscles and nerve irritation, frequently after an injury to the erect penis.

Priapism: Priapism is an erection that lasts longer than four hours or continues without sexual stimulation. The common low-flow form traps blood in the penis, is painful and is a medical emergency, because the tissue is starved of oxygen and permanent erectile damage can follow. It is a rare side effect of ED injections and tablets.

Peyronie’s Disease (PD): Peyronie’s Disease is a condition in which fibrous scar tissue, known as plaque, develops within the penis, often causing curvature and pain during erections.

Hypogonadism: Hypogonadism, or low testosterone, is a hormonal condition in which the body produces insufficient testosterone.

Late-Onset Hypogonadism: Late-Onset Hypogonadism is low testosterone that develops in middle-aged and older men together with symptoms such as reduced sex drive, erectile dysfunction, fatigue and loss of muscle, and affects around 2% of men aged 40 to 79 (European Male Ageing Study, NEJM 2010). It is distinct from the gradual fall in testosterone that comes with age alone and is often driven by obesity, type 2 diabetes or metabolic syndrome.

Testosterone Deficiency (TD): Testosterone Deficiency (TD) is the clinical term for low testosterone confirmed by blood tests and accompanied by symptoms. In the UK it is usually diagnosed from two early-morning blood samples showing total testosterone below 12 nmol/L (BSSM guidelines), and when ED is caused by TD, treating the deficiency may restore erections where tablets alone have not.

Conditions and Risk Factors Linked to Erectile Dysfunction

Diabetes: Diabetes is a chronic condition affecting blood sugar regulation and is a recognised risk factor for erectile dysfunction. Men with diabetes are around three times more likely to develop ED (Diabetes UK) and typically develop it 10 to 15 years earlier than men without it (NIDDK).

Type 2 Diabetes: Type 2 Diabetes is the form of diabetes in which the body stops responding properly to insulin, and it is the type most strongly linked to erectile dysfunction. Over time raised blood glucose damages the small blood vessels and nerves the penis depends on, and it is also associated with lower testosterone.

Diabetic Neuropathy: Diabetic Neuropathy is nerve damage caused by long-standing high blood glucose. When it affects the autonomic nerves that trigger an erection, the signal to relax the penile smooth muscle is weakened or lost, which is why ED in diabetes is often harder to treat than ED from poor blood flow alone.

Hypertension: Hypertension, or high blood pressure, is a condition in which the force of blood against artery walls is consistently elevated, contributing over time to the vascular changes associated with erectile dysfunction. Some blood pressure medicines can add to the problem, so the choice of tablet matters.

Cardiovascular Disease (CVD): Cardiovascular Disease (CVD) is the group of conditions affecting the heart and blood vessels, including heart attack and stroke, and it shares its root cause with erectile dysfunction. Because the penile arteries are far narrower than the coronary arteries, ED frequently appears three to five years before heart symptoms (Princeton Consensus), which is why new ED should prompt a cardiovascular check.

Coronary Artery Disease (CAD): Coronary Artery Disease (CAD) is the narrowing of the arteries that supply the heart muscle, caused by the same build-up of fatty plaque that narrows the arteries of the penis. In the COBRA study, two-thirds of men with coronary disease had developed ED first, on average three years before their heart symptoms (Montorsi et al., European Heart Journal 2006).

Atherosclerosis: Atherosclerosis is the build-up of plaque inside artery walls, which can restrict blood flow to the penis and contribute to erectile dysfunction.

Peripheral Arterial Disease (PAD): Peripheral Arterial Disease (PAD) is the narrowing of arteries outside the heart, most often in the legs and pelvis. When the arteries feeding the penis are affected, too little blood reaches the erectile tissue, and ED is often the first symptom to appear, well before leg pain on walking.

High Cholesterol: High Cholesterol is a raised level of fat in the blood, particularly LDL cholesterol, which deposits in artery walls and drives atherosclerosis. It damages the lining of the penile blood vessels and reduces the nitric oxide they produce, so erections become weaker long before cholesterol causes any heart symptoms.

Metabolic Syndrome: Metabolic Syndrome is a cluster of conditions that occur together: excess weight around the waist, raised blood pressure, raised blood glucose, raised triglycerides and low HDL cholesterol. Together, they damage blood vessel lining and lower testosterone, and men with the syndrome are more than twice as likely to develop erectile dysfunction (meta-analysis, Journal of Sexual Medicine 2015).

Obesity: Obesity is excess body fat, usually defined as a body mass index of 30 or more, and it raises the risk of erectile dysfunction in three ways at once: it damages the lining of blood vessels, it lowers testosterone because fat tissue converts it to oestrogen, and it drives the insulin resistance and inflammation that harm nerves and arteries. In a randomised trial, a third of obese men with ED regained normal erectile function after two years of diet and exercise alone (Esposito et al., JAMA 2004).

Obstructive Sleep Apnoea (OSA): Obstructive Sleep Apnoea (OSA) is a condition in which the airway repeatedly closes during sleep, interrupting breathing and starving the body of oxygen. The oxygen dips damage the blood vessel lining, the broken sleep suppresses the night-time erections that keep penile tissue healthy, and testosterone falls, so ED is common in men with untreated OSA and often improves with CPAP treatment.

Chronic Kidney Disease (CKD): Chronic Kidney Disease (CKD) is long-term loss of kidney function, and erectile dysfunction affects most men who have it, particularly on dialysis. The causes stack up: the diabetes and high blood pressure that damage the kidneys also damage the penile arteries; waste products build up and damage nerves, testosterone falls, and anaemia causes fatigue.

Depression: Depression is a persistent low mood and loss of interest that affects the brain chemistry controlling sexual desire and arousal, and it has a two-way relationship with erectile dysfunction: depression makes ED more likely, and living with ED commonly leads to depression. Many antidepressants, particularly SSRIs, add to the problem as a side effect.

Anxiety: Anxiety is a state of persistent worry or fear that keeps the body’s sympathetic “fight or flight” system switched on. An erection needs the opposite, parasympathetic state, so anxiety works directly against it by narrowing blood vessels and raising adrenaline. It is the most common cause of erectile dysfunction in younger men.

Stress: Stress is the body’s response to pressure, whether from work, money, relationships or health, and when it is prolonged, it raises adrenaline and cortisol, narrows blood vessels and lowers testosterone. Stress-related ED is common, often comes and goes with circumstances, and responds to treatment aimed at the nervous system as well as the erection itself.

Multiple Sclerosis (MS): Multiple Sclerosis (MS) is a condition in which the immune system damages the protective coating of nerves in the brain and spinal cord, and it causes erectile dysfunction in the majority of men who have it. MS lesions can block the nerve signals for an erection directly, while fatigue, spasticity, bladder symptoms and low mood add to the difficulty.

Parkinson’s Disease: Parkinson’s Disease is a progressive neurological condition that affects the autonomic nervous system and lowers dopamine in the brain, both of which are needed for a normal erection. Erectile dysfunction is one of its most common non-motor symptoms and can appear years before the movement problems are diagnosed.

Spinal Cord Injury: Spinal Cord Injury is damage to the spinal cord that interrupts the nerve pathways between the brain and the penis. The effect on erections depends on the level and completeness of the injury: men with higher injuries often keep reflex erections from touch but lose those triggered by arousal, while lower injuries can do the reverse. Most men with a spinal cord injury can still achieve erections with treatment.

Stroke: Stroke is the sudden loss of blood supply to part of the brain, and erectile dysfunction affects well over half of male stroke survivors. The stroke itself can damage the brain regions that control arousal, but the two conditions also share the same underlying vascular disease, so ED is sometimes the warning that arrives first.

Prostate Cancer: Prostate Cancer and its treatments, including surgery, radiotherapy and hormone therapy, can contribute to erectile dysfunction. Surgery can damage the nerves that run alongside the prostate, radiotherapy affects the blood vessels gradually over months, and hormone therapy lowers the testosterone that drives desire and erections.

Radical Prostatectomy: Radical Prostatectomy is the surgical removal of the whole prostate gland, usually for cancer, and is the single most common surgical cause of erectile dysfunction. Even when the surgeon spares the nerve bundles beside the prostate, they are bruised and stretched, and natural erections can take one to two years to return, during which the erectile tissue is at risk of scarring from lack of oxygen.

Benign Prostatic Hyperplasia (BPH): Benign Prostatic Hyperplasia (BPH) is non-cancerous enlargement of the prostate gland that becomes common after 50 and causes urinary symptoms. It does not cause erectile dysfunction directly, but the two occur together far more often than chance, and some BPH medicines (notably finasteride and dutasteride) and operations such as TURP can cause or worsen ED.

Lower Urinary Tract Symptoms (LUTS): Lower Urinary Tract Symptoms (LUTS) are the bladder and urination problems, such as a weak stream, urgency and getting up at night, that usually come from an enlarging prostate. Men with LUTS have a markedly higher rate of erectile dysfunction, and the worse the urinary symptoms, the worse the ED tends to be, because both share the same loss of nitric oxide and smooth muscle relaxation in the pelvis.

Hypothyroidism: Hypothyroidism is an underactive thyroid gland producing too little thyroid hormone. It lowers testosterone, raises prolactin and reduces nitric oxide, and so causes erectile dysfunction in around two-thirds of men with untreated hypothyroidism (Carani et al., JCEM 2005). Because it is easily detected on a blood test and treatable with thyroid hormone replacement, it should be checked in any man with unexplained ED.

Hyperthyroidism: Hyperthyroidism is an overactive thyroid gland producing too much thyroid hormone. It raises the protein that binds testosterone, increases its conversion to oestrogen and speeds up the whole body, including the nervous system, so erectile dysfunction, premature ejaculation and reduced desire are all more common. Erections usually recover once the thyroid is brought under control.

Hyperprolactinaemia: Hyperprolactinaemia is an abnormally high level of the hormone prolactin, most often caused by a benign pituitary growth (a prolactinoma) or by medicines such as antipsychotics. Excess prolactin switches off the signal that drives testosterone production, so it causes low desire and erectile dysfunction, and it is one of the hormonal causes a blood test can pick up and treat.

Sickle Cell Disease: Sickle Cell Disease is an inherited blood disorder in which misshapen red blood cells block small blood vessels. In the penis, this causes priapism, prolonged painful erections that starve the tissue of oxygen, and repeated episodes scar the erectile tissue, which is why erectile dysfunction is several times more common in men with the condition.

Smoking: Smoking is the single most preventable cause of erectile dysfunction. Nicotine and the chemicals in smoke narrow and stiffen the arteries, reduce the nitric oxide that lets the penis fill with blood and speed up atherosclerosis, raising the risk of ED by around half in current smokers (meta-analysis of 29 studies, Cao et al. 2013). The risk rises with every cigarette and every year, and falls again after stopping.

Excessive Alcohol Consumption: Excessive Alcohol Consumption affects erections in two ways. In the short term, alcohol dampens the nerve signals that start an erection and lowers blood pressure, so a single heavy session can cause a temporary failure. In the long term, regular drinking above the UK Chief Medical Officers’ guideline of 14 units a week lowers testosterone, damages nerves and liver function, and is an established cause of persistent erectile dysfunction.

Anabolic Androgenic Steroids (AAS): Anabolic Androgenic Steroids (AAS) are synthetic forms of testosterone taken to build muscle. They switch off the body’s own testosterone production and shrink the testicles, so while desire may be high during use, erectile dysfunction and low testosterone commonly follow when a course stops, and natural production can take months or years to recover.

Recreational Drugs: Recreational Drugs such as cocaine, amphetamines, MDMA, cannabis and opioids all interfere with erections by narrowing blood vessels, over-stimulating the stress response, blunting nerve signals or lowering testosterone. Occasional use causes temporary failure; regular use is an established cause of persistent erectile dysfunction, particularly in younger men.

Cycling-Related Erectile Dysfunction: Cycling-Related Erectile Dysfunction is ED caused by prolonged pressure from a bicycle saddle on the perineum, which compresses the pudendal nerve and the arteries that feed the penis. It is linked to long hours in the saddle, typically more than three hours a week (Massachusetts Male Aging Study), rather than moderate cycling, which is good for erections, and it usually improves with a cut-out saddle, a higher handlebar position and regular breaks.

Pelvic Trauma: Pelvic Trauma is injury to the pelvis, most often a fracture from a road accident or a fall from height, and it causes erectile dysfunction in a substantial proportion of men by tearing the arteries or nerves that run close to the pubic bone. Where the urethra is also injured the risk is higher still, and in younger men this is one of the few situations where surgical repair of the penile arteries may be considered.

Anatomy of the Penis and the Male Sexual System

Penis: The Penis is the male external sexual organ, made up of erectile tissue, skin, and a network of blood vessels and nerves. An erection depends on all three working together: nerves carrying the signal, arteries delivering the blood and the erectile tissue trapping it; erectile dysfunction can arise from a fault in any one of them.

Penile Shaft: The Penile Shaft is the main length of the penis, extending from the body to the glans. It contains the three columns of erectile tissue that fill with blood during an erection, and it is the area treated in focused shockwave therapy and examined for signs of Peyronie’s disease.

Glans Penis: The Glans is the sensitive, rounded tip of the penis. It is formed from the end of the corpus spongiosum rather than the main erectile chambers, which is why it stays softer than the shaft during an erection.

Corpora Cavernosa: The Corpora Cavernosa are a pair of spongy erectile tissue chambers running the length of the penis that fill with blood to produce an erection. Most physical causes of erectile dysfunction come down to either too little blood reaching these chambers or blood escaping from them too quickly.

Corpus Cavernosum: Corpus Cavernosum is the singular form of corpora cavernosa, referring to one of the two erectile chambers of the penis. The term appears in the names of several ED treatments and tests, including intracavernosal injections, which deliver medicine directly into the chamber.

Corpus Spongiosum: The Corpus Spongiosum is a column of erectile tissue that surrounds the urethra and keeps it open during erection.

Tunica Albuginea: The Tunica Albuginea is the tough, fibrous sheath surrounding the erectile tissue of the penis. As the chambers fill with blood, it stretches and compresses the veins that drain them, which is what traps the blood and gives an erection its rigidity. When it loses elasticity, through age, scarring or Peyronie’s disease, that seal weakens and erections become harder to keep.

Crura: The Crura of the Penis are the two internal, tapered columns of erectile tissue that anchor the penis to the pelvis. Because around a third of the penis lies inside the body at the crura, they are one reason the pelvic floor muscles around them matter for erection firmness.

Urethra: The Urethra is the tube that carries urine (and semen, during ejaculation) out of the body. In men it runs through the prostate and then along the underside of the penis inside the corpus spongiosum, which is why prostate surgery and some ED treatments, such as urethral pellets, involve it.

Cavernous Arteries: The Cavernous Arteries are the main blood vessels supplying the erectile tissue of the penis, and their function is central to achieving a firm erection. Their blood flow is what a penile Doppler ultrasound measures when investigating the cause of ED.

Internal Pudendal Artery: The Internal Pudendal Artery is the artery that carries most of the blood supply to the penis, branching from the main pelvic artery and dividing into the cavernous and dorsal arteries. Because it is narrow and runs close to the pelvic bone, it is vulnerable to both atherosclerosis and compression, for example, from a bicycle saddle.

Deep Dorsal Vein: The Deep Dorsal Vein is the main vein draining blood from the erectile tissue of the penis, running along the top of the shaft beneath its fibrous covering. During an erection, its flow is choked off by the swelling tissue, holding the blood in; in venous leak, this does not happen fully and the erection drains away.

Emissary Veins: The Emissary Veins are the small veins that pass at an angle through the tunica albuginea to drain blood out of the erectile chambers. When the chambers fill, they are flattened against the sheath and closed, trapping the blood; this is the veno-occlusive mechanism, and its failure is the basis of venous leak.

Cavernous Nerves: The Cavernous Nerves are the fine autonomic nerves that carry the erection signal into the erectile tissue, releasing the nitric oxide that starts the process. They run along the sides of the prostate gland, which is why they are so easily damaged in prostate surgery and why nerve-sparing techniques matter.

Pudendal Nerve: The Pudendal Nerve supplies sensation and movement to the genitals and pelvic floor and is central to normal erectile and urinary function. It carries the sensation that triggers reflex erections, and pressure on it, as in long-distance cycling, can cause numbness and erection problems.

Neurovascular Bundles: The Neurovascular Bundles are the paired groups of nerves and blood vessels running alongside the prostate and penis that carry the erection signal and blood supply. Preserving them is the aim of nerve-sparing prostatectomy, and how much of them survives surgery largely determines whether erections return.

Pelvic Floor Muscles: The Pelvic Floor Muscles support the pelvic organs and play a role in erectile and urinary function. Two of them wrap around the base of the penis and contract to hold blood in during an erection, so weak muscles contribute to ED and strengthening them, by exercise or magnetic stimulation, can improve rigidity.

Perineum: The Perineum is the area between the genitals and the anus, containing muscles and nerves important to sexual and urinary function. It is where saddle pressure in cycling acts, and where the focused shockwave handpiece is applied to reach the root of the penis.

Prostate Gland: The Prostate Gland sits below the bladder and surrounds part of the urethra; its treatment can sometimes contribute to erectile dysfunction. The nerves that control erection run along its surface, so surgery, radiotherapy and some prostate medicines all carry a risk to erectile function.

Testicles: The Testicles are the male reproductive organs responsible for producing sperm and testosterone. Their testosterone output supports libido and erectile tissue health, so conditions that shrink or damage them, including anabolic steroid use, are linked to ED.

Smooth Muscle Cells: Smooth Muscle Cells line the erectile tissue of the penis and must relax fully to allow blood to fill the penis during an erection. Their gradual replacement by scar tissue, through ageing, diabetes or lack of oxygen after prostate surgery, is one of the main reasons ED becomes permanent.

Trabecular Smooth Muscle: Trabecular Smooth Muscle is the network of involuntary muscle within the spongy framework of the erectile chambers. It is held tight while the penis is flaccid and relaxes under the influence of nitric oxide to let the chambers fill, and its health, measured as the proportion of muscle to scar tissue, is a key determinant of erectile function.

Autonomic Nervous System: The Autonomic Nervous System controls involuntary processes such as heart rate and blood flow, including the vascular responses involved in achieving an erection. Its two branches work in opposition: the parasympathetic branch starts an erection, and the sympathetic branch ends it, which is why stress and anxiety interfere so directly.

Parasympathetic Nervous System: The Parasympathetic Nervous System is the “rest and digest” branch of the autonomic nervous system and the one that produces an erection. Its nerves, running from the lower spinal cord through the cavernous nerves, release nitric oxide into the penis, relaxing the smooth muscle and opening the arteries.

Sympathetic Nervous System: The Sympathetic Nervous System is the “fight or flight” branch of the autonomic nervous system. It keeps the penis flaccid by holding the smooth muscle contracted, returns it to the flaccid state after ejaculation, and when over-activated by stress or anxiety, it prevents an erection from forming at all.

Hypothalamus: The Hypothalamus is the region at the base of the brain that links the nervous and hormonal systems. It starts the hormonal chain that leads to testosterone production and contains the centres that initiate erections in response to arousal, so disorders affecting it can cause both low testosterone and ED.

Pituitary Gland: The Pituitary Gland is the pea-sized gland beneath the brain that releases the hormones LH and FSH, which instruct the testicles to produce testosterone and sperm. Pituitary problems, including benign tumours that raise prolactin, are an important hormonal cause of ED and are detected on a blood test.

How an Erection Works: Core Erectile Function

Erection: An Erection is the stiffening and enlargement of the penis that occurs when its erectile chambers fill with blood. It needs a signal from the nerves, open arteries to deliver the blood, relaxed smooth muscle to receive it and a sheath that traps it, and erectile dysfunction is a failure at one or more of those steps.

Arousal: Arousal is the physical and emotional state of sexual excitement that prepares the body for sexual activity. It begins in the brain and is the trigger for an erection, which is why ED treatments such as PDE5 inhibitors do not work without it.

Libido: Libido is a person’s overall desire or drive for sexual activity, which can be affected by hormonal, psychological and physical factors. It is distinct from erectile function: a man can have a strong libido with ED, and loss of libido alongside ED often points to low testosterone or depression.

Tumescence: Tumescence is the medical term for the swelling of the penis as it fills with blood at the start of an erection, before it becomes fully rigid. The word appears in the test name nocturnal penile tumescence, which measures these swellings during sleep.

Detumescence: Detumescence is the return of the penis to its soft, flaccid state after an erection. It is brought about by the sympathetic nervous system contracting the smooth muscle, letting blood drain out; in ED it happens too early, and in priapism it fails to happen at all.

Flaccid: Flaccid describes the penis in its soft, resting state, when the smooth muscle in the erectile tissue is contracted and only a trickle of blood passes through. The flaccid state is the normal baseline from which an erection develops, and a penis that stays partly firm when it should be flaccid is a feature of hard flaccid syndrome.

Erectile Rigidity: Erectile Rigidity is the firmness of an erection, determined by the pressure of blood trapped in the erectile chambers. It is what the Erection Hardness Score grades from 1 to 4, and a grade 3 or above is usually needed for penetration.

Nocturnal Erections: Nocturnal Erections are the involuntary erections, usually three to five a night (ISSM), that occur during the dreaming phases of sleep. They keep the erectile tissue supplied with oxygen, and their presence or absence helps distinguish psychological from physical causes of erectile dysfunction.

Morning Erections: Morning Erections are the last of the night’s nocturnal erections, present on waking, when testosterone is at its daily peak. Losing them is one of the clearest signs that ED has a physical rather than psychological cause, and their return is often an early sign that treatment is working.

Nocturnal Penile Tumescence (NPT): Nocturnal Penile Tumescence (NPT) is the natural, involuntary erection that occurs during sleep, sometimes used to help distinguish physical from psychological causes of erectile dysfunction. It can be measured at home with a wearable sensor or in a sleep laboratory.

Psychogenic Erection: A Psychogenic Erection is one triggered by the brain, in response to sight, sound, thought or memory, with the signal travelling down the spinal cord to the penis. It is the type most affected by anxiety and stress, and by spinal injuries above the lower back.

Reflexogenic Erection: A Reflexogenic Erection is one produced by direct touch, through a reflex loop in the lowest part of the spinal cord that does not need the brain. It explains why many men with spinal cord injuries can still achieve erections, and why physical stimulation sometimes succeeds when arousal alone does not.

Sexual Response Cycle: The Sexual Response Cycle is the sequence the body passes through during sex, usually described as desire, arousal, orgasm and resolution. Erectile dysfunction is a problem of the arousal phase, and distinguishing it from problems of desire or orgasm is part of a proper assessment.

Smooth Muscle Relaxation: Smooth Muscle Relaxation is the loosening of the muscle fibres within the erectile tissue and artery walls that allows blood to flood into the penis. It is set off by nitric oxide and sustained by cGMP, and every oral ED medicine works by prolonging it.

Corporal Veno-Occlusive Mechanism: The Corporal Veno-Occlusive Mechanism is the process by which the swelling erectile chambers press the draining veins shut against the tunica albuginea, sealing blood inside the penis. It is what turns a swollen penis into a rigid one, and when it fails, the result is venous leak.

Nitric Oxide (NO): Nitric Oxide is a signalling molecule that triggers the relaxation of blood vessels in the penis, allowing the increased blood flow needed for an erection. It is produced by nerve endings and by the lining of healthy blood vessels, and reduced nitric oxide is the common thread linking diabetes, smoking and high cholesterol to ED.

Nitric Oxide-cGMP Pathway: The Nitric Oxide–cGMP Pathway is the chain of chemical signals that produces an erection: nerves and blood vessel lining release nitric oxide, which activates an enzyme that makes cGMP, which relaxes the smooth muscle. PDE5 inhibitors such as sildenafil work at the end of this chain by stopping cGMP from being broken down.

Cyclic Guanosine Monophosphate (cGMP): cGMP is a molecule that relaxes the smooth muscle of the penis to allow blood flow in during an erection; PDE5 inhibitor medications work by preserving cGMP levels for longer.

Phosphodiesterase Type 5 (PDE5): PDE5 is an enzyme found in penile tissue that regulates blood flow; PDE5 inhibitor medications work by blocking this enzyme to help maintain an erection.

Guanylate Cyclase: Guanylate Cyclase is the enzyme inside penile smooth muscle cells that nitric oxide switches on, and which then produces the cGMP that relaxes the muscle. Drugs that stimulate it directly are used for other conditions and must never be combined with PDE5 inhibitors because of the risk of a dangerous fall in blood pressure.

Neurotransmitters: Neurotransmitters are the chemical messengers nerves use to communicate. In erection, nitric oxide and acetylcholine carry the “go” signal and noradrenaline carries “stop”, while in the brain, dopamine promotes and serotonin dampens sexual response, which is why antidepressants that raise serotonin often cause ED.

Endothelium: The Endothelium is the single layer of cells lining the inside of every blood vessel, including those in the penis. Far from being passive, it produces the nitric oxide that opens the arteries for an erection, and damage to it from smoking, diabetes or high cholesterol is the earliest stage of vascular ED.

Endothelial Function: Endothelial Function describes how well the thin layer of cells lining blood vessels works to regulate blood flow, which is a key factor in achieving a healthy erection. Because the penile arteries are so small, a decline in endothelial function shows up as ED years before it causes heart symptoms.

Blood Flow, Vascular Health and Erectile Dysfunction

Penile Blood Flow: Penile Blood Flow is the circulation of blood into and out of the penis that determines whether it is flaccid or erect. An erection raises inflow many times over while outflow is sealed off, and penile Doppler ultrasound measures the speed of that inflow to diagnose vascular ED.

Vasodilation: Vasodilation is the widening of blood vessels that allows increased blood flow into the penis during arousal, a necessary step in achieving an erection.

Vasoconstriction: Vasoconstriction is the narrowing of blood vessels as the muscle in their walls tightens. In the penis it is the normal resting state and the way an erection ends, but when driven by stress hormones, nicotine, cold or stimulant drugs it can stop an erection from forming.

Arterial Insufficiency: Arterial Insufficiency occurs when narrowed or blocked blood vessels reduce blood flow to the penis, a recognised physical cause of erectile dysfunction. On a penile Doppler scan, it shows as a low peak inflow speed.

Venous Leak: Venous Leak is a vascular cause of erectile dysfunction in which blood drains from the penis too quickly through the veins to maintain a firm erection. Men with venous leak can often get an erection but lose it within a minute or two, and it responds less well to tablets than arterial ED.

Veno-Occlusive Dysfunction (VOD): Veno-Occlusive Dysfunction, also known as venous leak, occurs when the veins of the penis fail to trap blood effectively, causing it to escape too quickly to sustain an erection.

Endothelial Dysfunction: Endothelial dysfunction is a condition in which the thin inner lining of the blood vessels loses its ability to release nitric oxide and relax normally. Because the penile arteries depend heavily on this lining to widen, endothelial dysfunction is one of the earliest changes behind vascular erectile dysfunction.

Microcirculation: Microcirculation refers to blood flow through the smallest vessels, including capillaries and arterioles, which is important for tissue health and erectile function.

Microvascular Disease: Microvascular disease is damage to the body’s smallest arteries and capillaries, most often caused by long-standing diabetes or high blood pressure. In the penis it reduces blood flow and oxygen supply to the erectile tissue, which is a major reason why ED is so common in men with diabetes.

Angiogenesis: Angiogenesis is the formation of new blood vessels, a process some treatments, such as shockwave therapy, aim to stimulate in order to improve blood supply.

Neovascularisation: Neovascularisation is the growth of a new network of blood vessels within tissue that has become short of oxygen or blood supply. In erectile dysfunction it describes the improved blood supply to the corpora cavernosa that regenerative treatments are intended to produce.

Oxidative Stress: Oxidative stress is an imbalance in which harmful oxygen molecules (free radicals) outnumber the body’s antioxidant defences. In the penis it breaks down nitric oxide before it can relax the erectile tissue, and it is a common thread linking smoking, diabetes and ageing to erectile dysfunction.

Hypoxia: Hypoxia is a shortage of oxygen in the tissues. The flaccid penis is naturally low in oxygen, and regular erections, including those during sleep, are what re-oxygenate the erectile tissue; prolonged hypoxia encourages fibrosis and the loss of healthy smooth muscle.

Cavernosal Fibrosis: Cavernosal fibrosis is the replacement of the elastic smooth muscle inside the corpora cavernosa with stiff collagen scar tissue. Once established it prevents the erectile tissue from expanding fully and trapping blood, so it is a leading cause of erectile dysfunction that no longer responds to tablets.

Penile Fibrosis: Penile fibrosis is the general term for scar tissue forming anywhere within the penis, whether in the erectile chambers, the tunica albuginea or around the blood vessels. It can follow injury, prolonged erection, repeated injections or long periods without erections, and it stiffens the tissue in a way that impairs erectile function.

Collagen: Collagen is the body’s most abundant structural protein, giving tissues their strength and flexibility.

Cardiovascular Risk Assessment: Cardiovascular risk assessment is the process of estimating a man’s chance of heart attack or stroke from his blood pressure, cholesterol, blood sugar, weight, smoking history and family history. It is recommended for every man presenting with erectile dysfunction, because the same arterial disease that causes ED often appears in the heart two to five years later (Princeton Consensus).

Sentinel Symptom: A sentinel symptom is an early warning sign that appears before a more serious illness declares itself. Erectile dysfunction is widely regarded as a sentinel symptom for cardiovascular disease because narrowing of the small penile arteries typically shows up years before the same process affects the larger arteries of the heart.

Hormones, Testosterone and Erectile Dysfunction

Testosterone: Testosterone is the primary male sex hormone, playing a central role in libido, erectile function, and overall reproductive health.

Total Testosterone (TT): Total testosterone is the full amount of testosterone in the blood, including both protein-bound and freely available testosterone.

Free Testosterone: Free testosterone is the portion of testosterone in the blood that is not bound to protein and is immediately available for the body to use.

Bioavailable Testosterone: Bioavailable testosterone is the testosterone that tissues can actually use: the free fraction plus the portion loosely attached to albumin, which releases easily. It is often a better guide than total testosterone in men whose SHBG is high or low, such as those who are older, obese or diabetic.

Sex Hormone-Binding Globulin (SHBG): SHBG is a protein produced by the liver that binds to sex hormones, including testosterone, regulating how much is available for the body to use.

Luteinising Hormone (LH): Luteinising hormone (LH) is released by the pituitary gland and instructs the Leydig cells of the testes to produce testosterone. Measuring LH alongside testosterone shows whether low testosterone originates in the testes themselves (high LH) or in the brain and pituitary (low or normal LH).

Follicle-Stimulating Hormone (FSH): Follicle-stimulating hormone (FSH) is a pituitary hormone that acts on the Sertoli cells of the testes to drive sperm production. It is usually measured with LH as part of a hormone profile, and a raised FSH points to primary testicular failure rather than a problem higher up in the hormonal chain.

Prolactin: Prolactin is a hormone produced by the pituitary gland; elevated levels can sometimes contribute to reduced libido and erectile difficulties.

Oestrogen: Oestrogen is present in men in smaller amounts than testosterone but still plays an important role in sexual function and overall health.

Cortisol: Cortisol is the body’s primary stress hormone; chronically elevated levels can negatively affect testosterone production and sexual function.

Dehydroepiandrosterone (DHEA): DHEA is a natural steroid hormone your body uses as a building block to produce testosterone and other sex hormones.

Thyroid-Stimulating Hormone (TSH): Thyroid-stimulating hormone (TSH) is the pituitary signal that controls the thyroid gland, and a TSH blood test is the standard way of detecting an under- or overactive thyroid. Both thyroid disorders can cause erectile dysfunction and reduced desire, and both are usually reversible once the thyroid is treated.

Hypothalamic-Pituitary-Gonadal Axis: The hypothalamic-pituitary-gonadal (HPG) axis is the hormonal chain of command that governs testosterone production: the hypothalamus releases GnRH, which prompts the pituitary to release LH and FSH, which in turn stimulate the testes. A fault at any level, from stress and illness to pituitary tumours, can lower testosterone and affect erections.

Andropause: Andropause, sometimes called the “male menopause”, is the popular name for the gradual decline in testosterone that occurs with age, at roughly 1% a year from a man’s thirties onward (BAUS). Unlike the female menopause it is slow and does not affect every man, and the medical term for a clinically significant fall is late-onset hypogonadism.

Testosterone Replacement Therapy (TRT): Testosterone replacement therapy (TRT) is the prescribed use of testosterone gel, injections or other preparations to restore levels in men with confirmed hypogonadism. It improves desire, energy and mood, and can help erections in men with low testosterone, but it is not a treatment for erectile dysfunction in men whose testosterone is normal.

Erectile Dysfunction Questionnaires and Assessment Tools

International Index of Erectile Function (IIEF): The International Index of Erectile Function (IIEF) is a validated 15-question questionnaire that measures five areas of male sexual function: erection, orgasm, desire, intercourse satisfaction and overall satisfaction. It is the standard outcome measure used in clinical trials of ED treatments.

International Index of Erectile Function-5 (IIEF-5): IIEF-5 is a short, 5-question survey used to screen for and measure the severity of erectile dysfunction.

Sexual Health Inventory for Men (SHIM): The Sexual Health Inventory for Men (SHIM) is the name under which the IIEF-5 questionnaire is commonly used in clinics. Its five questions produce a score from 5 to 25, with 21 or below suggesting erectile dysfunction and lower bands indicating mild, moderate or severe ED.

Erection Hardness Score (EHS): The Erection Hardness Score is a simple 4-point scale used by clinicians and patients to assess and track erection firmness.

Sexual Encounter Profile (SEP): The Sexual Encounter Profile (SEP) is a short diary a man completes after each sexual attempt during a trial or treatment. Its two most important questions ask whether he was able to penetrate his partner (SEP2) and whether his erection lasted long enough for successful intercourse (SEP3).

Global Assessment Question (GAQ): The Global Assessment Question (GAQ) is a single yes-or-no question asked at the end of treatment: has the treatment improved your erections? It is a simple way of capturing a man’s own verdict alongside the more detailed questionnaire scores.

Ageing Males’ Symptoms Scale (AMS): The Ageing Males’ Symptoms (AMS) scale is a 17-question survey that scores the psychological, physical and sexual symptoms associated with falling testosterone. It is used to assess men suspected of late-onset hypogonadism and to track their response to treatment.

QRISK3: QRISK3 is the cardiovascular risk calculator used across the NHS to estimate a person’s chance of a heart attack or stroke over the next ten years. Erectile dysfunction is one of the factors built into QRISK3, which reflects how strongly ED predicts future heart disease.

Princeton Consensus: The Princeton Consensus is a series of expert recommendations, most recently Princeton IV, on assessing heart health in men with erectile dysfunction and on the safety of sexual activity. Its central message is that ED should prompt a cardiovascular risk assessment, because it often precedes a heart event by three to five years.

Massachusetts Male Ageing Study (MMAS): The Massachusetts Male Aging Study (MMAS) is the landmark population study that first measured how common erectile dysfunction is, finding that 52% of men aged 40 to 70 had some degree of ED. Its figures remain the most widely quoted prevalence data in the field.

Erectile Dysfunction Tests and Diagnostics

Physical Examination: A physical examination for erectile dysfunction is a brief, routine check in which the clinician measures blood pressure and weight, feels the pulses, and examines the penis and testicles for structural or hormonal clues. It is quick and painless, and it helps decide which blood tests or scans are needed.

Genital Examination: A genital examination is the part of the physical assessment in which the clinician inspects the penis for scar tissue, curvature or skin changes and checks the size and consistency of the testicles. Small testicles can suggest low testosterone, while a hard plaque points towards Peyronie’s disease.

Digital Rectal Examination (DRE): A digital rectal examination (DRE) is a brief check in which the clinician feels the prostate through the wall of the rectum with a gloved, lubricated finger. It is included in an ED assessment when there are urinary symptoms or when prostate disease is suspected, as the two conditions often occur together in older men.

Blood Pressure Measurement: Blood pressure measurement is a routine part of every ED assessment because high blood pressure stiffens and narrows arteries, and the small arteries of the penis are often the first to be affected. Some blood pressure medicines can also contribute to ED, so the reading helps guide treatment choices.

Testosterone Blood Test: A testosterone blood test measures the level of the main male hormone in a sample of blood. It is recommended for every man with erectile dysfunction (EAU guidelines), not because low testosterone is usually the cause, but because when it is present, treating it can restore desire and improve the response to other ED treatments.

Morning Testosterone Test: A morning testosterone test is a blood sample taken between roughly 7 and 11 am, when testosterone is at its daily peak and laboratory reference ranges apply. A low result should always be confirmed with a second morning sample before a diagnosis of hypogonadism is made.

Glycated Haemoglobin (HbA1c): HbA1c is a blood test that reflects average blood sugar over the previous two to three months. It is used in ED assessment to detect undiagnosed or poorly controlled diabetes, which damages both the blood vessels and nerves of the penis and makes ED around three times more likely (Diabetes UK).

Fasting Blood Glucose: A fasting blood glucose test measures blood sugar after at least eight hours without food and is a simple way of screening for diabetes or pre-diabetes. Because erectile dysfunction can be the first sign of undiagnosed diabetes, it forms part of the standard blood tests for ED.

Lipid Profile: A lipid profile is a blood test that measures total cholesterol, LDL (“bad”) and HDL (“good”) cholesterol and triglycerides. Raised cholesterol contributes to the arterial plaque that narrows penile blood vessels, so the result is used both to explain ED and to estimate a man’s wider cardiovascular risk.

Full Blood Count (FBC): A full blood count (FBC) is a general blood test that measures red cells, white cells and platelets. In an ED work-up, it checks for anaemia or inflammation, which can sap energy and sexual function, and it provides a baseline before treatments such as testosterone, which can thicken the blood.

Thyroid Function Tests: Thyroid function tests measure TSH and thyroid hormone levels to detect an underactive or overactive thyroid gland. Both conditions can cause erectile dysfunction, loss of desire and changes to ejaculation, and both usually improve once the thyroid is treated.

Prostate-Specific Antigen (PSA): PSA (prostate-specific antigen) is a protein made by the prostate that is measured by a blood test. It is not a test for erectile dysfunction, but it is often checked in older men with ED and urinary symptoms, and it is required before starting testosterone therapy.

Hormone Profile: A hormone profile is a panel of blood tests, usually total and free testosterone, SHBG, LH, FSH, prolactin and sometimes oestradiol and thyroid hormones, taken in the morning. Looking at these together shows not only whether testosterone is low but where in the hormonal chain the problem lies.

Penile Doppler Ultrasound: Penile Doppler ultrasound is a specialised scan used to assess blood flow and tissue structure within the penis, helping to identify whether erectile dysfunction is caused by poor arterial inflow, a venous leak or scarring.

Intracavernosal Injection Test: The intracavernosal injection test involves inducing an erection with medication in a clinical setting so that blood flow and erectile function can be properly assessed.

Cavernosometry: Cavernosometry is a specialist test that measures the pressure inside the erectile chambers while saline is infused to maintain an erection. If high flow rates are needed to keep the penis rigid, blood is escaping too quickly, which confirms a venous leak.

Cavernosography: Cavernosography is an imaging test in which X-ray contrast is injected into the erectile chambers so that the veins draining the penis can be seen. It is usually performed alongside cavernosometry to pinpoint exactly where a venous leak is occurring.

Penile Arteriography: Penile arteriography is an X-ray study of the arteries supplying the penis, performed by injecting contrast through a fine catheter. It is reserved for younger men with ED after pelvic or perineal injury in whom a single arterial blockage might be repaired surgically.

Penile Biothesiometry: Penile biothesiometry is a diagnostic test measuring nerve sensitivity in the penis, used to assess whether reduced sensation or nerve damage is contributing to erectile dysfunction.

RigiScan: RigiScan is a portable device worn overnight that records how often the penis becomes erect during sleep and how rigid each erection is. It provides objective evidence of whether the erectile mechanism is physically intact.

Adam Sensor: The Adam Sensor is a wearable band worn at the base of the penis overnight that records the number, timing and duration of night-time erections and sends the results to a smartphone app. It gives men a simple way to track their nocturnal erections at home over weeks or months and to see whether they are improving.

Nocturnal Erection Monitoring: Nocturnal erection monitoring is the recording of erections that occur naturally during sleep, either with a RigiScan or a simpler stamp or snap-gauge test. Normal night-time erections in a man who cannot achieve them when awake point towards a psychological rather than physical cause.

Erectile Dysfunction Treatments and Technology

Lifestyle Changes: Lifestyle changes are the first-line measures recommended for every man with erectile dysfunction: stopping smoking, losing excess weight, exercising regularly, moderating alcohol and improving sleep. Because they tackle the vascular causes of ED directly, they improve both erections and the response to other treatments.

Pelvic Floor Exercises: Pelvic floor exercises strengthen the bulbocavernosus and ischiocavernosus muscles at the base of the penis, which help trap blood and maintain rigidity. A randomised UK trial found that 40% of men with ED regained normal function after three months of supervised exercises (Dorey et al., BJGP 2004).

Psychosexual Therapy: Psychosexual therapy is specialist talking therapy that addresses the anxiety, relationship difficulties and unhelpful beliefs that cause or maintain erectile dysfunction. It is the main treatment for psychogenic ED and is often combined with medical treatment when both physical and psychological factors are present.

Cognitive Behavioural Therapy (CBT): Cognitive behavioural therapy (CBT) is a structured, short-term talking therapy that helps a man identify and change the thought patterns that trigger performance anxiety. For erectile dysfunction it focuses on breaking the cycle of anticipating failure, monitoring the erection during sex and avoiding intimacy.

Sensate Focus: Sensate focus is a series of structured touching exercises for couples, developed by Masters and Johnson, in which intercourse is initially off-limits so that the pressure to perform is removed. It is one of the most widely used techniques in psychosexual therapy for erectile dysfunction.

Phosphodiesterase Type 5 Inhibitors (PDE5 Inhibitors): Phosphodiesterase type 5 inhibitors (PDE5 inhibitors) are the tablets most commonly prescribed for erectile dysfunction, including sildenafil, tadalafil, vardenafil and avanafil. They work by blocking the enzyme that breaks down cGMP, so the erectile tissue stays relaxed and filled with blood for longer, but they only work in response to sexual arousal, and around 30–35% of men do not respond adequately (EAU guidelines).

Sildenafil: Sildenafil is a PDE5 inhibitor medication used to treat erectile dysfunction, taken about an hour before sex and effective for around four hours. It is the active ingredient in Viagra and is also available over the counter in the UK as Viagra Connect.

Tadalafil: Tadalafil is a long-acting PDE5 inhibitor medication used to treat erectile dysfunction, remaining effective for up to 36 hours and also available as a low daily dose. It is the active ingredient in Cialis and is also licensed for urinary symptoms caused by an enlarged prostate.

Vardenafil: Vardenafil is a PDE5 inhibitor medication used to treat erectile dysfunction.

Avanafil: Avanafil is a fast-acting PDE5 inhibitor medication used to treat erectile dysfunction.

Viagra: Viagra is the original brand name for sildenafil, launched by Pfizer in 1998 as the first tablet for erectile dysfunction. It remains the best-known ED treatment, although generic sildenafil is identical in effect and considerably cheaper.

Viagra Connect: Viagra Connect is the over-the-counter version of sildenafil 50 mg, which UK pharmacists have been able to sell without a prescription since 2018 after a short suitability check. It is identical to prescription sildenafil at the same dose.

Cialis: Cialis is the brand name for tadalafil, sometimes called the “weekend pill” because a single dose can work for up to 36 hours. It is available as an on-demand tablet or a low-dose daily tablet, and generic tadalafil is now widely available.

Daily Tadalafil: Daily tadalafil is a low dose (2.5 mg or 5 mg) taken every day rather than before sex, so that a steady level of the medicine is always present. It allows spontaneity, is often used in penile rehabilitation after prostate surgery, and also relieves urinary symptoms from an enlarged prostate.

Nitrates: Nitrates are heart medicines such as GTN spray and isosorbide mononitrate, used to treat angina, that work by releasing nitric oxide. They must never be combined with PDE5 inhibitors, because the two together can cause a sudden and dangerous fall in blood pressure; recreational “poppers” carry the same risk.

Alprostadil: Alprostadil is a synthetic form of prostaglandin E1 that relaxes the erectile tissue and widens the penile arteries directly, so unlike tablets it does not depend on sexual arousal or intact nerves. It is used as an injection (Caverject), a urethral pellet (MUSE) or a cream (Vitaros) when PDE5 inhibitors are unsuitable or ineffective.

Intracavernosal Injection (ICI): Intracavernosal injection (ICI) is the self-injection of a small dose of alprostadil or a combination of vasodilators into the side of the penis shortly before sex. It produces an erection in 5 to 15 minutes in most men, including many who do not respond to tablets, and it is taught in clinic before home use.

Caverject: Caverject is the brand name for alprostadil in an injectable form, supplied as a dual-chamber pen that mixes the dose before use. It is the most commonly prescribed intracavernosal injection in the UK.

Medicated Urethral System for Erection (MUSE): Medicated urethral system for erection (MUSE) is a small pellet of alprostadil inserted into the opening of the urethra with a disposable applicator. It avoids needles, although it is generally less effective than injection and can cause a burning sensation.

Vitaros: Vitaros is a prescription cream containing alprostadil that is applied to the tip of the penis 5 to 30 minutes before sex. It offers a needle-free alternative for men who cannot take tablets, with an erection typically lasting one to two hours.

Eroxon: Eroxon is a drug-free gel, available over the counter in UK pharmacies since 2023, that is massaged onto the head of the penis for about 15 seconds. It works by a rapid cooling-then-warming effect that stimulates the nerve endings, and its maker reports an erection within 10 minutes in around 65% of users (Haleon clinical data).

Vacuum Erection Device (VED): A vacuum erection device uses gentle suction to draw blood into the penis and can support erectile function and tissue health. We use the SOMAerect device, and the pump can either produce an erection for sex or be used daily as part of penile rehabilitation.

Constriction Ring: A constriction ring is a soft, stretchy ring placed at the base of the penis to slow the outflow of blood and keep an erection firm. It is used with a vacuum device or on its own for men with mild venous leak and should not be left on for more than 30 minutes.

Penile Traction Therapy: Penile traction therapy uses a mechanical device to apply gentle, sustained stretching to the penis. In erectile dysfunction, it is used mainly to prevent the loss of length and the fibrosis that can follow prostate surgery or long periods without erections.

RestoreX: RestoreX is the penile traction device we use to apply gentle, sustained stretching as part of a treatment plan. In men with ED, it is used for 30 to 60 minutes a day, most often after prostate surgery, to maintain length and tissue health.

Focused Shockwave Therapy (f-ESWT): Focused shockwave therapy (f-ESWT) uses targeted acoustic waves to stimulate blood flow and the growth of new blood vessels in the erectile tissue. It is the only ED treatment aimed at the underlying cause rather than the symptom, and a 2025 Cochrane review of 21 sham-controlled trials found it improves erectile function in men with vascular ED. Full details are on our Focused Shockwave Therapy page.

Low-Intensity Extracorporeal Shockwave Therapy (Li-ESWT): Low-intensity extracorporeal shockwave therapy (Li-ESWT) is the term used in the research literature for shockwave treatment of erectile dysfunction, where the energy is far lower than that used to break up kidney stones. Focused Li-ESWT is the form tested in most clinical trials and is recognised by the European Association of Urology as a treatment option for vascular ED.

Duolith SD1 T-Top: The Duolith SD1 T-Top is the focused shockwave device made by Storz Medical of Switzerland that we use for every ED shockwave treatment. It has been used in more sham-controlled trials of ED than any other single device, and its adjustable energy and depth allow the treatment to be tailored to each man.

Extracorporeal Magnetotransduction Therapy (EMTT): EMTT is a non-invasive treatment using high-energy magnetic pulses intended to stimulate tissue repair and improve microcirculation, delivered without touching the skin. We use it alongside focused shockwave therapy; evidence for EMTT in erectile dysfunction is still developing and further research is continuing. See our EMTT page for how the treatment is delivered.

 NanoVi Exo: NanoVi Exo is a non-invasive medical device that delivers humidified air carrying a specific electromagnetic signal to help the body repair proteins damaged by oxidative stress. The signal mirrors the wavelengths produced naturally during cellular repair, supporting the refolding of oxidatively damaged proteins. NanoVi is used in regenerative and men’s health settings, including erectile dysfunction and Peyronie’s disease treatment, where oxidative stress contributes to vascular damage and scar tissue formation. A session involves breathing normally through a nasal tube for 15 to 20 minutes.

Tesla Chair: The Tesla Chair is a treatment chair that uses functional magnetic stimulation to contract the pelvic floor muscles thousands of times in a 30-minute session while the patient remains fully clothed. It strengthens the muscles that support erectile rigidity and is used in our programmes for men with pelvic floor weakness, ED after prostate surgery or urinary symptoms.

Functional Magnetic Stimulation (FMS): Functional magnetic stimulation (FMS) is the technology behind the Tesla Chair: pulsed electromagnetic fields pass through clothing and tissue to make the pelvic floor muscles contract and relax repeatedly. It achieves in one session what would take thousands of voluntary pelvic floor exercises.

NESA X-Signal: NESA X-Signal is a non-invasive neuromodulation device that delivers very low-intensity microcurrents through electrodes on the wrists and ankles to help rebalance the autonomic nervous system. Because erections depend on the parasympathetic “rest” branch of that system, it is used in our programmes for men whose ED is linked to stress, anxiety or poor sleep.

E-Shot: The E-Shot is the name of a platelet-rich plasma (PRP) injection treatment for erectile dysfunction, in which growth factors concentrated from the patient’s own blood are injected into the erectile tissue to encourage repair. It is offered as one element of a multimodal programme rather than as a stand-alone cure, and the evidence base is still developing.

Platelet-Rich Plasma (PRP): PRP therapy uses a concentrated preparation of a patient’s own blood platelets to help stimulate tissue repair.

ED360: ED360 is MansMatters’ comprehensive, multimodal treatment programme for erectile dysfunction, combining focused shockwave therapy, EMTT, NanoVi Exo and other therapies tailored to each patient. 

Penile Rehabilitation: Penile rehabilitation is a structured recovery programme, usually following prostate surgery, designed to keep the erectile tissue healthy and oxygenated while the nerves recover. It typically combines a vacuum device, daily tadalafil and, in our clinic, focused shockwave therapy, and is best started within the first few months after surgery.

Penile Implant: Penile implant surgery places a medical device inside the penis to restore erectile function when all other treatments have failed. It is permanent and irreversible, but satisfaction rates above 90% are reported for both patients and partners (BAUS).

Inflatable Penile Prosthesis (IPP): An inflatable penile prosthesis (IPP) is the most commonly used type of penile implant, consisting of two cylinders in the erectile chambers, a small pump in the scrotum and a fluid reservoir in the abdomen. Squeezing the pump produces a natural-feeling erection and a release valve returns the penis to a flaccid state.

Malleable Penile Prosthesis: A malleable penile prosthesis is a simpler type of implant made of two bendable silicone rods that are positioned by hand, upwards for intercourse and downwards at other times. It has fewer mechanical parts than an inflatable device but leaves the penis permanently semi-rigid.

Penile Revascularisation: Penile revascularisation is a microsurgical bypass operation that connects an artery from the abdominal wall to the arteries of the penis to restore blood flow. It is suitable only for a small group of young men whose ED follows a specific arterial injury, and it is not recommended for ED caused by general arterial disease.

Taking the Next Step

Understanding the terminology surrounding erectile dysfunction can make it easier to research the condition, make sense of your test results and weigh up the treatment options. If you are finding it harder to get or keep an erection, have noticed your morning erections fading, or have been told that tablets are not working for you, MansMatters can help. Our CQC-registered clinic in Knightsbridge, London, provides confidential assessments and a range of non-surgical treatments tailored to each patient. Contact MansMatters to arrange a consultation and take the next step towards understanding and treating your symptoms.

This glossary is for general information and does not replace an individual assessment. It is reviewed every six months by our clinical team in line with our Editorial Policy. If you think anything on this page is inaccurate or out of date, please email us.