Testosterone Replacement Therapy Improves Metabolic Parameters in Hypogonadal Men with Type 2 Diabetes but Not in Men with Coexisting Depression: The BLAST Study

INTRODUCTION: The association between testosterone deficiency and insulin resistance in men with type 2 diabetes is well established and current endocrine society guidelines recommend the measurement of testosterone levels in all men with type 2 diabetes or erectile dysfunction. AIM: We report the first double-blind, placebo-controlled study conducted exclusively in a male type 2 diabetes population to assess metabolic changes with long-acting testosterone undecanoate (TU). METHODS: The type 2 diabetes registers of seven general practices identified 211 patients for a 30-week double-blind, placebo-controlled study of long-acting TU 1,000 mg followed by 52 weeks of open-label use. Because of the established impact of age, obesity, and depression on sexual function, these variables were also assessed for influence on metabolic parameters. MAIN OUTCOME MEASURE: Changes in glycated hemoglobin (HbA1c) and the level of testosterone at which response are achieved. RESULTS: Treatment with TU produced a statistically significant reduction in HbA1c at 6 and 18 weeks and after a further 52 weeks of open-label medication most marked in poorly controlled patients with baseline HbA1c greater than 7.5 where the reduction was 0.41% within 6 weeks, and a further 0.46% after 52 weeks of open-label use. There was significant reduction in waist circumference, weight, and body mass index in men without depression, and improvements were related to achieving adequate serum levels of testosterone. There were no significant safety issues. CONCLUSIONS: Testosterone replacement therapy significantly improved HbA1c, total cholesterol, and waist circumference in men with type 2 diabetes. Improvements were less marked in men with depression at baseline, and therapeutic responses were related to achieving adequate serum testosterone levels. Current advice on 3- to 6-month trials of therapy may be insufficient to achieve maximal response. Patients reported significant improvements in general health.