A 66-year-old man visits his family physician with complaints of urinary frequency, hesitancy, and dysuria. Digital rectal examination reveals an enlarged prostate, and the consistency is rubbery and nodular. Serum PSA is modestly increased. Which of the following is most closely related to the pathogenesis of the likely disorder described here?

DHT is a major growth factor for prostatic tissue. It is derived from the conversion from testosterone by the action of the enzyme 5a-reductase, type 2. Pharmaceutical inhibition of this enzyme is useful in the medical management of BPH. Estrogens also play an indirect role by stimulating the production of DHT receptors. hCG and a-fetoprotein are serum tumor markers for testicular cancers and bear no relevanceto BPH.