Relationship among serum testosterone, sexual function, and response to treatment in men receiving dutasteride for benign prostatic hyperplasia

Context: Although benign prostatic hyperplasia (BPH) is an androgen-dependent disorder, little is known regarding the influence of serum testosterone levels on sexual or prostate function or clinical response to dutasteride. Objective: The objective of the study was to explore these relationships in a large cohort of men treated with dutasteride for BPH. Design, Setting, Patients, and Outcome Measures: Among 4254 men with BPH participating in 2-yr placebo-controlled dutasteride trials, 27% had a pretreatment serum testosterone less than 300 ng/dl. These 1162 men were divided into seven groups based on their serum testosterone level (<150, 150-174, 175-199, 200-224, 225-249, 250-274, and 275-299 ng/dl) and compared with men with normal baseline serum testosterone (BST; ≥ 300 ng/dl). Questionnaires were used to assess sexual function, prostate-specific antigen (PSA), and prostate volume to assess androgenic stimulation of the prostate and the American Urological Association Symptom Index to assess clinical responses. Results: Although lower BST was associated with increased sexual dysfunction, this increase was not seen until BST was less than 225 ng/dl. There was no decrease in baseline PSA and prostate volume at low BST levels. Dutasteride was effective at decreasing PSA and prostate volume and improving BPH symptoms at all BST levels. Conclusions: In men with BPH, the frequency of sexual dysfunction increases at serum testosterone concentrations less than 225 ng/dl. However, PSA and prostate volume were similar at all testosterone levels, explaining why BPH can occur in men that would otherwise be considered hypogonadal. The fact that dutasteride is also effective in men with normal and low testosterone levels suggests that the high levels of 5α-reductase and dihydrotestosterone in the prostate allow the development and progression of prostatic hyperplasia, even at low circulating testosterone levels.