Aim: To explore the metabolic phenotype of obesity-related secondary hypogonadism (SH) in men pre-replacement and post-replacement therapy with long-acting intramuscular (IM) testosterone undecanoate (TU).
Methods: A prospective observational pilot study on metabolic effects of TU IM in male obesity-related SH (hypogonadal [HG] group, n = 13), including baseline comparisons with controls (eugonadal [EG] group, n = 15). Half the subjects (n = 7 in each group) had type 2 diabetes mellitus (T2D). Baseline metabolic assessment on Human Metabolism Research Unit: fasting blood samples; BodPod (body composition), and; whole-body indirect calorimetry. The HG group was treated with TU IM therapy for 6-29 months (mean 14.8-months [SD 8.7]), and assessment at the Human Metabolism Research Unit repeated. T-test comparisons were performed between baseline and follow-up data (HG group), and between baseline data (HG and EG groups). Data reported as mean (SD).
Results: Overall, TU IM therapy resulted in a statistically significant improvement in HbA1C (9 mmol/mol, P = 0.03), with 52% improvement in HOMA%B. Improvement in glycaemic control was driven by the HG subgroup with T2D, with 18 mmol/mol [P = 0.02] improvement in HbA1C. Following TU IM therapy, there was a statistically significant reduction in fat mass (3.5 Kg, P = 0.03) and increase in lean body mass (2.9 kg, P = 0.03). Lipid profiles and energy expenditure were unchanged following TU IM therapy. Comparisons between baseline data for HG and EG groups were equivalent apart from differences in testosterone, SHBG and basal metabolic rate (BMR).
Conclusion: In men with obesity-related SH (including a subgroup with T2D), TU IM therapy improved glycaemic control, beta cell function, and body composition.
Keywords: Male obesity-associated secondary hypogonadism; Obesity; Secondary Hypogonadism; Testosterone; Testosterone replacement; Type 2 Diabetes Mellitus.