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Probability diagnosis


Drugs esp. excess alcohol

Diabetes (autonomic dysfunction)


Serious disorders not to be missed


  • Generalised arteriopathy esp. lower limbs


  • Generalised: viral, bacterial


  • Pituitary fossa


  • Systemic illness

  • Chronic kidney disease

Pitfalls (often missed)

Pelvic trauma

Excessive cigarette smoking

Iatrogenic e.g. prostate surgery, drugs

Thrombosis corpus callosum


  • Neurological e.g. MS

  • Hypogonadism e.g. Klinefelter’s

  • Anatomical e.g. tight frenulum, Peyroine’s disease

Masquerades checklist

Depression including drugs


Drugs: various

Thyroid/other endocrine: several (see history)

Spinal dysfunction e.g. spinal cord pathology, cauda equina lesion

Is the patient trying to tell me something?

Consider psychosexual dysfunction incl. marital disharmony, performance anxiety

Key history

  • Nature of onset including nature of sexual relationship

  • Ask about nocturnal and early morning erections

  • Drug history incl. alcohol, nicotine (4 times risk), street drugs (cocaine, cannabis), pharmaceutical agents esp. antihypertensives (beta blockers, diuretics), hypolipidaemic agents, antiandrogens (prostate cancer treatment), antidepressants, antipsychotics, H2-receptor antagonists

Key examination

Genitourinary, cardiovascular and neurogenic examinations are important. This should include a rectal examination; examination of the vascular and neurological status of the lower limbs; and genitalia esp. the testicles and penis. Check the cremasteric and bulbocavernosus reflexes.

Key investigations

First line:

  • glucose

  • FBE

  • free testosterone (androgen deficiency)

  • thyroxine (hypothyroidism)

  • prolactin

  • LH

  • FSH

  • Urinalysis


  • LFTs esp. GGT (alcohol effect) and KFTs

  • nocturnal penile tumescence

  • Doppler flow studies

Diagnostic tips

Endocrine causes to consider include androgen/testosterone deficiency, hyperprolactinaemia and hypothyroidism. Consider pituitary fossa tumour.

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