What is the cause of benign prostatic hyperplasia?

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Last updated: September 28, 2026 • View editorial policy

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What Causes Benign Prostatic Hyperplasia?

Benign prostatic hyperplasia (BPH) is a multifactorial condition of unknown exact etiology that requires testosterone and results from an imbalance between cellular growth and apoptosis (programmed cell death) in the prostatic transition zone, favoring excessive cellular proliferation. 1

The Hormonal Mechanism

The pathophysiology centers on the androgen pathway:

  • Testosterone is absolutely required for BPH to develop, though testosterone itself does not directly cause BPH 1
  • The enzyme 5α-reductase (types I and II) converts testosterone to dihydrotestosterone (DHT) within prostate tissue
  • DHT is the key driver: It has higher affinity for androgen receptors and is the more potent androgenic hormone that promotes prostatic growth 1
  • The testosterone/DHT-androgen receptor complex enters the cell nucleus and initiates DNA transcription, leading to cellular proliferation 1

Critical distinction: While androgens are necessary for BPH development, they are not the etiological (causative) factors for BPH initiation 2. No evidence supports that testosterone or DHT levels trigger the onset of BPH.

The Growth-Death Imbalance

BPH develops because cellular growth outpaces cellular death (apoptosis), resulting in net accumulation of glandular epithelial tissue, smooth muscle, and connective tissue specifically in the prostatic transition zone 1.

Contributing Factors Beyond Hormones

While the exact trigger remains unidentified, several factors contribute:

  • Aging: The single most consistent risk factor—BPH prevalence increases from 40-45 years onward, reaching 60% by age 60 and 80% by age 80 1
  • Chronic inflammation: Lymphocytic infiltration with proinflammatory cytokines damages epithelial and stromal cells 2, 3
  • Urinary toxins: Years of exposure to uncharacterized urinary substances may disrupt stromal/epithelial homeostasis in the transition zone 2
  • Estrogens: May participate in nodular stromal cell proliferation in some patients 2
  • Growth factors: Basic fibroblast growth factor (bFGF) and transforming growth factor beta (TGF-β1) promote stromal proliferation 3
  • Metabolic factors: Obesity and metabolic syndrome are increasingly recognized as preceding factors 2, 4

The Anatomic Specificity

BPH exclusively occurs in the transition zone surrounding the urethra 2. This anatomic specificity suggests that local factors—particularly chronic exposure to urine and subsequent inflammation—play a critical role in initiating the cellular damage that DHT then amplifies into hyperplastic growth.

Clinical Implications

Understanding causation matters for treatment: 5α-reductase inhibitors (finasteride, dutasteride) work by blocking DHT synthesis, addressing the hormonal amplification of prostatic growth 4. However, they don't address the initial trigger, which is why they're most effective for larger prostates (>30cc) where hormonal proliferation is more established 1.

Common pitfall: Assuming low testosterone causes BPH or that testosterone replacement will worsen it—neither is supported by evidence. The issue is local DHT production and the growth-apoptosis imbalance, not systemic testosterone levels.

References

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