The long-term effect of specific type II 5α-reductase inhibition with finasteride on bone mineral density in men: Results of a 4-year placebo controlled trial

Purpose: We determine the effect of long-term suppression of dihydrotestosterone with finasteride, a specific type II 5α-reductase inhibitor, on bone mineral density. Materials and Methods: As part of a large (3,040 cases) 4-year, double-blind, placebo controlled trial designed to assess the long-term effects of finasteride in men with benign prostatic hyperplasia, 157 men 46 to 76 years old who were randomized to receive either 5 mg. finasteride or placebo underwent dual energy x-ray absorptiometry of the lumbar spine at baseline and at years 2, 3 and 4. Results: Of 117 patients who had a baseline measurement and at least 1 additional measurement during the study baseline mean plus or minus standard deviation bone mineral density values were 1.12 ± 0.17 gm./cm.² in the finasteride group (63) and 1.10 ± 0.17 gm./cm.² in the placebo group (54). After 4 years bone mineral density was not different between treatment groups (finasteride 1.14 ± 0.17 gm./cm.² and placebo 1.13, ± 0.18 gm./cm.²). Similar results were obtained for the 33 finasteride and 25 placebo treated patients who completed the study with year 4 bone mineral density measurements. Conclusions: These data demonstrate that long-term inhibition of type II 5α-reductase with finasteride does not adversely affect bone mineral density.