Haider KS, Haider A, Saad F, et al. - This prospective registry study was undertaken to determine if testosterone therapy (TTh) in men with hypogonadism and type 2 diabetes mellitus (T2DM) improves glycaemic control and insulin sensitivity, and results in remission of T2DM. In total, 356 men who had total testosterone levels ≤ 12.1 nmol/L (350 ng/dL) and symptoms of hypogonadism were involved and followed up for 11 years. All patients received standard diabetes treatment and additionally, 178 patients received 1,000 mg parenteral testosterone undecanoate every 12 weeks after an initial period of 6 weeks. A control group included 178 patients with hypogonadal conditions who opted not to receive TTh. Over the treatment period, patients with hypogonadism and T2DM treated with testosterone reported significant progressive and sustained reductions in fasting glucose, glycated haemoglobin, and fasting insulin. The testosterone‐treated group had fewer deaths, myocardial infarctions, strokes, and diabetic complications. Long‐term TTh improves glycaemic control and insulin resistance in men with T2DM and hypogonadism. Diabetes remission occurred in one‐third of the patients. TTh is potentially a novel alternative therapy for people with T2DM and hypogonadism.