Last reviewed 01/2018

Aetiology is multifactorial. Increased risk of BPH is seen with advancing age, endogenous androgens and prostate volume, black men (while Asian men have a lower risk) (1).

The hormonal theory postulates that nodular hyperplasia is due to an increased oestrogen to testosterone ratio which is associated with ageing. The oestrogen enhances the expression of receptors for dihydrotestosterone, derived from plasma testosterone, which mediates prostatic growth.

In support of this theory:

  • nodular hyperplasia occurs only in the presence of an intact testis
  • levels of plasma testosterone are similar in those with and without the disease, and decline after the age of 60 years (2)

The neoplastic theory proposes that enlargement is due to a fibromyoadenoma i.e. a benign neoplasm of fibrous, muscle, and glandular tissue

As the size of the prostate does not linearly correlate with clinical features, enhanced prostatic smooth muscle tone and an irritable bladder wall have been postulated as features which trigger symptoms.


  1. Mangera A, Chapple C. Clinical Review: Benign prostatic hyperplasia. GPOnline 2012
  2. Drug and Therapeutics Bulletin (1995). 33(3): 19-21