Testosterone therapy to prevent type 2 diabetes mellitus in at-risk men (T4DM): Design and implementation of a double-blind randomised controlled trial.

Background Low circulating testosterone is associated with an increased risk of developing type 2 diabetes (T2DM) in overweight men with impaired glucose tolerance (IGT). Aims To determine in a multi-centre, double-blinded placebo-controlled randomized trial whether testosterone treatment combined with lifestyle intervention (Weight Watchers) relative to lifestyle intervention alone reduces T2DM incidence and improves glucose tolerance at 2 years. Study population Overweight or obese men aged 50-74 years with a serum testosterone of <= 14 nmol/L and IGT or newly diagnosed T2DM established by an oral glucose tolerance test (OGTT). Setting, drug and protocol Six Australian capital city-based tertiary care centres. Participants were randomized 1:1 and injected with testosterone undecanoate (1000 mg/4 mL) or vehicle (4 mL castor oil), at baseline, 6 weeks and 3-monthly thereafter. Primary endpoints (a) Proportion of participants with 2-hour OGTT >= 11.1 mmol/L at 2 years, and (b) a difference at 2 years >= 0.6 mmol/L in the mean 2-hour OGTT glucose between treatments. Secondary endpoints Fasting insulin, HbA1c, body composition, maximal handgrip strength; sexual function and lower urinary tract symptoms; serum sex steroids and sex hormone binding globulin; mood and psychosocial function; adherence to lifestyle intervention; and healthcare utilization and costs. Safety Overseen by an Independent Data Safety Monitoring Committee. Haematocrit, lipids and prostate-specific antigen (PSA) are assessed 6-monthly and information relating to haematological, urological and cardiovascular adverse events from each clinic visit. Sub-studies (a) Changes in bone density and micro-architecture, (b) motivation and behaviour, (c) telomere length, (d) extended treatment up to 4 years, and (e) hypothalamo-pituitary testicular axis recovery at treatment end.