# Glossary

> Plain-English definitions of the clinical, anatomical and regulatory terms used across ED medicine.

- **Source:** ED Treatment Guides (https://www.edtreatmentguides.com/glossary)
- **Terms:** 66

## Anatomy & physiology

- **Corpora cavernosa** (also: corpus cavernosum) — The two cylinders of spongy erectile tissue running the length of the penis. They do essentially all the work of an erection. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Corpus spongiosum** — The third, smaller cylinder on the underside of the penis carrying the urethra. It stays softer during an erection so ejaculation is not obstructed. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Tunica albuginea** — The tough fibrous sheath around each corpus cavernosum. It is what makes an erection rigid rather than merely swollen, and the structure that scars in Peyronie's disease. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Cavernosal arteries** — The arteries supplying blood to the erectile tissue. At roughly 1–2 mm across they are much narrower than the coronary arteries, which is why they show vascular disease first. See https://www.edtreatmentguides.com/causes/cardiovascular-disease.
- **Veno-occlusive mechanism** (also: venous occlusion) — The process by which expanding erectile tissue compresses the outflow veins against the tunica albuginea, trapping blood and producing rigidity. Its failure is venous leak. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Cyclic GMP** (also: cGMP) — The signalling molecule that relaxes smooth muscle in the penis and allows blood in. PDE5 inhibitors work by preventing its breakdown. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Nitric oxide** (also: NO) — The messenger released by nerve endings and blood vessel lining during arousal. It triggers the cascade that produces an erection. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Endothelium** — The single-cell lining of blood vessels, which produces nitric oxide. Endothelial dysfunction is the shared mechanism linking ED with cardiovascular disease. See https://www.edtreatmentguides.com/causes/cardiovascular-disease.
- **Cavernous nerves** (also: neurovascular bundles) — The parasympathetic nerves that trigger an erection. They run alongside the prostate, which is why prostate surgery so often affects erectile function. See https://www.edtreatmentguides.com/causes/prostate-treatment.
- **Ischiocavernosus** — A pelvic floor muscle at the base of the penis that raises internal pressure beyond what blood flow alone achieves. It is trainable. See https://www.edtreatmentguides.com/treatments/pelvic-floor-therapy.
- **Reflexogenic erection** — An erection triggered by direct physical stimulation through a spinal reflex, without needing a signal from the brain. Often preserved after spinal cord injury. See https://www.edtreatmentguides.com/causes/neurological-conditions.
- **Psychogenic erection** — An erection triggered by thought, sight or arousal in the brain rather than by touch. See https://www.edtreatmentguides.com/guides/how-erections-work.
- **Nocturnal penile tumescence** (also: NPT, morning wood, morning erections) — Erections occurring during REM sleep, typically three to five a night. Their presence indicates the physical mechanism is intact. See https://www.edtreatmentguides.com/guides/morning-erections.
- **Detumescence** — The return to a flaccid state, driven by noradrenaline from the sympathetic nervous system contracting the smooth muscle. See https://www.edtreatmentguides.com/guides/how-erections-work.

## Conditions & causes

- **Erectile dysfunction** (also: ED, impotence) — The persistent inability to get or keep an erection firm enough for satisfactory sex. The usual clinical threshold is difficulty on most attempts over about three months. See https://www.edtreatmentguides.com/guides/symptoms-and-diagnosis.
- **Venous leak** (also: veno-occlusive dysfunction) — Failure to trap blood in the penis, producing an erection that starts well then fades within a minute or two. See https://www.edtreatmentguides.com/treatments/constriction-rings.
- **Priapism** — An erection lasting more than four hours. A medical emergency — go to an emergency department, as delay risks permanent tissue damage. See https://www.edtreatmentguides.com/guides/pde5-safety.
- **Peyronie's disease** — Fibrous scar tissue in the tunica albuginea causing penile curvature, pain and often erectile dysfunction. See https://www.edtreatmentguides.com/causes/peyronies-disease.
- **Hypogonadism** (also: low testosterone, low T) — Deficient testosterone production. Diagnosis requires two low morning blood tests plus matching symptoms. See https://www.edtreatmentguides.com/causes/low-testosterone.
- **Hyperprolactinaemia** (also: high prolactin) — Raised prolactin, which suppresses testosterone production. Causes include medication, underactive thyroid and a benign pituitary tumour. See https://www.edtreatmentguides.com/causes/thyroid-and-prolactin.
- **Prolactinoma** — A benign pituitary tumour that secretes prolactin. Usually treated with dopamine agonists rather than surgery. See https://www.edtreatmentguides.com/causes/thyroid-and-prolactin.
- **Atherosclerosis** — Plaque build-up narrowing arteries. Because penile arteries are narrow, it causes symptoms there before the heart or brain. See https://www.edtreatmentguides.com/causes/cardiovascular-disease.
- **Metabolic syndrome** — The cluster of central obesity, raised blood pressure, raised glucose and abnormal lipids. Strongly associated with erectile dysfunction. See https://www.edtreatmentguides.com/causes/obesity.
- **Autonomic neuropathy** — Damage to the involuntary nerves, commonly from diabetes. It interrupts the signal that starts an erection, which is why tablets work less well. See https://www.edtreatmentguides.com/causes/diabetes.
- **Neuropraxia** — Temporary loss of nerve function from stretching or bruising rather than division. It explains why erectile function can recover over 12–24 months after nerve-sparing prostate surgery. See https://www.edtreatmentguides.com/causes/prostate-treatment.
- **Performance anxiety** (also: spectatoring) — Anxiety about sexual performance that activates the sympathetic nervous system — the exact chemical signal that ends an erection. See https://www.edtreatmentguides.com/causes/performance-anxiety.
- **Obstructive sleep apnoea** (also: OSA, sleep apnea) — Repeated airway collapse during sleep. It fragments REM, suppresses testosterone and damages blood vessels — a commonly missed cause of ED. See https://www.edtreatmentguides.com/causes/sleep-apnea.
- **Retrograde ejaculation** — Semen passing backwards into the bladder rather than out. Common after prostate surgery and often mistaken for erectile dysfunction. See https://www.edtreatmentguides.com/causes/prostate-treatment.
- **Autonomic dysreflexia** — A dangerous blood pressure surge triggered by stimulation below a spinal cord injury at or above T6, including sexual activity. Needs a plan agreed in advance. See https://www.edtreatmentguides.com/causes/neurological-conditions.
- **Benign prostatic hyperplasia** (also: BPH, enlarged prostate) — Non-cancerous prostate enlargement causing urinary symptoms. Daily tadalafil is licensed to treat both BPH and ED. See https://www.edtreatmentguides.com/compare/daily-vs-on-demand.
- **NAION** (also: non-arteritic anterior ischaemic optic neuropathy) — Sudden painless vision loss in one eye. A very rare adverse effect associated with PDE5 inhibitors; previous episodes are a contraindication. See https://www.edtreatmentguides.com/guides/side-effects.

## Treatments & medication

- **PDE5 inhibitor** (also: phosphodiesterase type 5 inhibitor) — The drug class including sildenafil, tadalafil, vardenafil and avanafil. They block the enzyme that breaks down cyclic GMP. See https://www.edtreatmentguides.com/treatments/sildenafil.
- **Sildenafil** (also: Viagra) — The original PDE5 inhibitor. Onset 30–60 minutes, useful window 4–6 hours, and inexpensive as a generic. See https://www.edtreatmentguides.com/treatments/sildenafil.
- **Tadalafil** (also: Cialis) — A long-acting PDE5 inhibitor with a useful window up to 36 hours, and the only one with a licensed daily dose. See https://www.edtreatmentguides.com/treatments/tadalafil.
- **Vardenafil** (also: Levitra, Staxyn) — A PDE5 inhibitor similar in duration to sildenafil. Carries a QT-interval caution that the others do not. See https://www.edtreatmentguides.com/treatments/vardenafil.
- **Avanafil** (also: Stendra) — The newest and most selective PDE5 inhibitor, with the fastest onset — as little as 15 minutes — and the highest price. See https://www.edtreatmentguides.com/treatments/avanafil.
- **Alprostadil** (also: prostaglandin E1, Caverject, Edex, MUSE) — A vasodilator given by penile injection, as a urethral pellet or as a cream. It works directly on the erectile tissue without needing a nerve signal. See https://www.edtreatmentguides.com/treatments/penile-injections.
- **Trimix** (also: bimix) — A compounded injectable mixture of papaverine, phentolamine and alprostadil. Effective at lower doses of each, so less painful than alprostadil alone. See https://www.edtreatmentguides.com/treatments/penile-injections.
- **Intracavernosal injection** (also: ICI, penile injection) — Injection of medication directly into the erectile tissue. Success rates of 70–90%+, including in men for whom tablets failed. See https://www.edtreatmentguides.com/treatments/penile-injections.
- **Vacuum erection device** (also: VED, penis pump) — A cylinder and pump that draws blood into the penis mechanically, held by a constriction ring. Works independently of nerves and arteries. See https://www.edtreatmentguides.com/treatments/vacuum-erection-device.
- **Constriction ring** (also: tension ring, cock ring) — A ring at the base of the penis that slows blood leaving it. Maximum 30 minutes of use. See https://www.edtreatmentguides.com/treatments/constriction-rings.
- **Penile prosthesis** (also: penile implant, inflatable penile prosthesis, IPP) — Surgically implanted cylinders that restore rigidity. The highest satisfaction rate of any ED treatment, and irreversible. See https://www.edtreatmentguides.com/treatments/penile-implants.
- **Penile rehabilitation** — Using medication, a vacuum device or injections after prostate surgery to keep erectile tissue oxygenated while nerves recover. See https://www.edtreatmentguides.com/causes/prostate-treatment.
- **Testosterone replacement therapy** (also: TRT) — Treatment for confirmed testosterone deficiency. It suppresses sperm production, so fertility must be discussed before starting. See https://www.edtreatmentguides.com/treatments/testosterone-therapy.
- **hCG** (also: human chorionic gonadotropin) — Stimulates the testicles to produce their own testosterone while preserving sperm production. Used off-label where fertility matters. See https://www.edtreatmentguides.com/guides/ed-and-fertility.
- **Clomiphene** (also: clomifene) — Raises the body's own testosterone by blocking oestrogen feedback at the pituitary. Fertility-preserving, and used off-label in men. See https://www.edtreatmentguides.com/guides/ed-and-fertility.
- **Li-ESWT** (also: shockwave therapy, low-intensity extracorporeal shockwave therapy) — Acoustic pressure waves applied to the penis, intended to stimulate new blood vessel growth. Classed as investigational and not FDA-approved for ED. See https://www.edtreatmentguides.com/treatments/shockwave-therapy.
- **Platelet-rich plasma** (also: PRP, P-Shot) — Concentrated platelets from your own blood, injected into the penis. Not FDA-approved for ED, and sham-controlled evidence has not shown clear benefit. See https://www.edtreatmentguides.com/treatments/prp-therapy.
- **Sensate focus** — A structured programme of graded touching exercises with intercourse initially off the table. Removing the goal removes the performance test. See https://www.edtreatmentguides.com/treatments/sex-therapy.
- **Nitrates** — Drugs including nitroglycerin and isosorbide, plus recreational 'poppers'. Absolutely contraindicated with any PDE5 inhibitor. See https://www.edtreatmentguides.com/guides/pde5-safety.
- **Alpha-blocker** — Drugs such as tamsulosin and doxazosin for prostate or blood pressure symptoms. They lower blood pressure, so PDE5 inhibitors need careful dose separation. See https://www.edtreatmentguides.com/guides/pde5-safety.
- **CYP3A4 inhibitor** — Drugs including ketoconazole, ritonavir and clarithromycin that slow the breakdown of PDE5 inhibitors, raising blood levels and requiring dose reduction. See https://www.edtreatmentguides.com/guides/pde5-safety.

## Tests & measurements

- **IIEF-5** (also: SHIM, Sexual Health Inventory for Men) — A five-question screening questionnaire scoring erectile function from 5 to 25. Describes severity; it is not a diagnosis. See https://www.edtreatmentguides.com/tools/ed-self-assessment.
- **Penile duplex Doppler ultrasound** — An ultrasound measuring penile blood flow after an injected vasodilator. Used to distinguish arterial insufficiency from venous leak. See https://www.edtreatmentguides.com/guides/symptoms-and-diagnosis.
- **HbA1c** — A blood test reflecting average glucose over about three months. Used to screen for diabetes, a leading cause of ED. See https://www.edtreatmentguides.com/causes/diabetes.
- **LH and FSH** (also: luteinising hormone, follicle-stimulating hormone) — Pituitary hormones measured alongside testosterone. A low testosterone with low or normal LH points upstream to the pituitary rather than the testicles. See https://www.edtreatmentguides.com/causes/thyroid-and-prolactin.
- **SHBG** (also: sex hormone binding globulin) — The protein that binds testosterone in the blood. Useful when total testosterone is borderline, particularly in obesity or diabetes. See https://www.edtreatmentguides.com/causes/low-testosterone.
- **Haematocrit** — The proportion of blood made up of red cells. Monitored during testosterone therapy because the treatment can raise it to unsafe levels. See https://www.edtreatmentguides.com/treatments/testosterone-therapy.

## Commercial & regulatory

- **Bioequivalence** — The standard a generic must meet: the same rate and extent of absorption as the original, within defined limits. See https://www.edtreatmentguides.com/compare/brand-vs-generic.
- **Compounded medication** — A preparation mixed by a pharmacy to a prescription. Legal, but not FDA-approved for that formulation — which covers most chewable ED products and trimix. See https://www.edtreatmentguides.com/bluechew-reviews.
- **FDA-registered vs FDA-approved** — Registration is an administrative listing by the manufacturer. Approval or clearance means the FDA has actually evaluated the product. Marketing frequently blurs the two. See https://www.edtreatmentguides.com/treatments/constriction-rings.
- **De Novo pathway** — An FDA route to market for novel low-to-moderate risk devices with no existing equivalent. Used by some newer topical ED products. See https://www.edtreatmentguides.com/treatments/topical-treatments.
- **Prior authorisation** — Insurer approval required before a treatment is covered. The most common obstacle to second- and third-line ED treatment. See https://www.edtreatmentguides.com/guides/insurance-appeals.
- **Step therapy** — An insurance requirement to try cheaper treatments first. Documenting those failures is what unlocks the next step. See https://www.edtreatmentguides.com/guides/insurance-appeals.
- **Formulary** — The list of drugs a plan or pharmacy covers or stocks. ED medication is excluded from many US formularies entirely. See https://www.edtreatmentguides.com/guides/cost-and-insurance.
- **Sponsored link** (also: affiliate link, rel=sponsored) — A monetised link. FTC guidance requires clear disclosure before the reader clicks, and the rel attribute signals the paid relationship to search engines. See https://www.edtreatmentguides.com/how-we-make-money.

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_This page is general health information, not medical advice. It cannot account for your own history, medications or risk factors. Talk to a licensed clinician before starting, stopping or changing any treatment._

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