Double-blind placebo-controlled study of testosterone patch therapy on bone turnover in men with borderline hypogonadism.

Clinical studies suggest there may be a threshold concentration of serum testosterone below which replacement will result in skeletal and psychological benefit. We evaluated the response to testosterone in men with borderline hypogonadism. A randomized double-blind placebo-controlled trial in 39 men over age 40 years presenting with sexual dysfunction and a borderline low testosterone level (total testosterone <10 nmol/L or free androgen index <30%). Patients were randomized to Testoderm TTS body patch (5 mg/day, n = 20) or a placebo patch (n = 19) for 6 months, followed by open-label testosterone replacement for a further 6 months in all patients. During the placebo-controlled phase of the study serum testosterone increased significantly on testosterone vs. placebo treatment (p = 0.004); this was associated with a decrease in total body fat mass (p = 0.019) and increase in haemoglobin level (p = 0.036). There were no significant changes in lean body mass, markers of bone turnover, and measures of bone mineral density (BMD). There was evidence of difference in quality of life according to the Male Erectile Dysfunction Quality of Life questionnaire (MEDQoL score, p = 0.017), mainly accounted for by deterioration in the placebo arm. When the active treatment period was combined for placebo and testosterone groups, the within-patient analysis showed a significant effect of testosterone to decrease markers of bone resorption (uNTX/Cr, p = 0.007; iFDPD/Cr, p = 0.0006) and to increase lean body mass (p = 0.001). There was little convincing evidence from this study that testosterone replacement is likely to have major benefit in men over age 40 years with borderline hypogonadism and sexual dysfunction. However, there was evidence of suppression in bone resorption and hence longer and larger studies are needed to examine its effect on BMD.