(HealthDay News) – Men receiving testosterone supplementation who also receive dutasteride, which blocks the conversion of testosterone to its potent metabolite 5α-dihydrotestosterone (DHT), do not experience a significant difference in changes in muscle-related measures or sexual function compared to men receiving testosterone without dutasteride, according to a study published in the March 7 issue of the Journal of the American Medical Association.
Shalender Bhasin, MD, of the Boston University School of Medicine, and colleagues conducted a controlled trial of 102 healthy men (aged 18–50 years) who were randomly allocated to one of eight treatment groups. Participants received 50mg/week, 125mg/week, 300mg/week, or 600mg/week of testosterone enanthate for 20 weeks plus placebo (four groups) or 2.5mg/day of dutasteride (four groups).
The researchers found no significant dose-adjusted differences in fat-free mass between the dutasteride and placebo groups (P=0.18). For men receiving 50mg/week, 125mg/week, 300mg/week, and 600mg/week testosterone enanthate, the mean fat-free mass gained by the dutasteride and placebo groups was 0.6kg and 0.8kg, 2.6kg and 3.5kg, 5.8kg and 5.7kg, and 7.1kg and 8.1kg, respectively. There were no between-group differences in changes in fat mass, muscle strength, sexual function, prostate volume, sebum production, and hematocrit and lipid levels.
“Changes in fat-free mass in response to graded testosterone doses did not differ in men in whom DHT was suppressed by dutasteride from those treated with placebo, indicating that conversion of testosterone to DHT is not essential for mediating its anabolic effects on muscle,” the authors write.
One author disclosed financial ties to the pharmaceutical industry. GlaxoSmithKline and ENDO Pharmaceuticals provided the study drugs.