Effect of the dual 5α-reductase inhibitor, dutasteride, on serum testosterone and body mass index in men with benign prostatic hyperplasia

OBJECTIVE To investigate the effects of dutasteride on serum testosterone level and body mass index (BMI) in men who received medical therapy for benign prostatic hyperplasia (BPH). PATIENTS AND METHODS In all, 120 patients with BPH were randomized to three treatment groups: tamsulosin 0.2 mg/day (alpha-blocker group), dutasteride 0.5 mg/day (dutasteride group), or tamsulosin 0.2 mg plus dutasteride 0.5 mg/day (combination group) for 1 year. For all patients the BMI and serum testosterone levels were checked at baseline and after 1 year of treatment. RESULTS Among the evaluable 107 patients, the dutasteride (33) and combination groups (37) had significantly greater increases in serum testosterone level (16.3% and 15%, respectively) than the alpha-blocker group (37; 0.3%) after 1 year of treatment (both P < 0.001). When analysed by baseline serum testosterone tertile, the increases in serum testosterone level among the dutasteride and combination group were greatest in the lowest tertile. For BMI, the dutasteride and combination group had mean decreases of 0.17 and 0.20 kg/m2, respectively, at 1 year, whereas the alpha-blocker group had a mean increase of 0.04 kg/m2. The decreases in BMI for the dutasteride and combination group were statistically significant only in the lowest tertile (P = 0.048 and 0.010, respectively). CONCLUSION Our results show that dutasteride treatment in men with BPH led to a significant increase in serum testosterone level and a significant decrease in BMI among those with relatively lower baseline serum testosterone levels.