Does prostatic 5-alpha-reductase convert testosterone to DHT and support BPH growth?

The claim accurately describes the core prostatic androgen pathway. Local conversion of testosterone to DHT and DHT-mediated androgen-receptor (AR) activation are well established; evidence that this signaling supports BPH growth is strongest for an indirect epithelial-growth pathway and more provisional for stromal expansion.

Clinical and mechanistic evidence

• Human prostatectomy tissue directly demonstrates 5α-reduction of testosterone to DHT. Both membrane-associated, NADPH-dependent isoenzymes—SRD5A1 and SRD5A2—are present in prostate tissue; SRD5A2 is generally predominant in non-cancerous prostate, while SRD5A1 is mainly epithelial and SRD5A2 occurs in epithelial and stromal compartments in BPH.
• DHT is a potent direct AR agonist. It binds the AR ligand-binding domain and dissociates approximately 3–5 times more slowly than testosterone, promoting chaperone release, nuclear localization, receptor dimerization, and androgen-response-element-dependent transcription.
• In human-tissue-derived BPH cells, DHT increased stromal FGF-10 expression 5.3-fold at 100 pM. Stromal FGF-10 then stimulated epithelial-cell proliferation, supporting a paracrine stromal-to-epithelial route by which DHT/AR signaling can contribute to glandular growth. DHT did not directly stimulate epithelial or stromal proliferation in that study.

Clinical relevance

• Clinical suppression of DHT formation supports the pathway’s importance to overall BPH growth: in summarized placebo-controlled dutasteride trials, prostate volume fell 20.4%, whereas placebo-group volume increased 12.4%. 5α-reductase inhibitors also reduce BPH progression, urinary retention, and surgery risk in men with enlarged prostates.
• Stromal AR expression, inflammatory-cell recruitment, CCL3 signaling, and stromal proliferation form a biologically coherent model, but direct human evidence that AR activation independently drives stromal expansion is less definitive.

Bottom line

• The claim is substantially supported: prostatic 5α-reductase generates DHT, DHT activates AR, and this signaling contributes to BPH growth—particularly through stromal FGF-10–mediated epithelial proliferation—while the specific causal role in stromal growth remains plausible rather than firmly established.