The impact of testosterone replacement therapy on endothelial function in hypogonadal men with type 2 diabetes
Marija Pfeifer, Anze Resman & Rok Dezman
Background: Cross sectional studies in type 2 diabetic men have shown the 50% prevalence of hypogonadism. Testosterone deficiency worsens glycaemic control and accelerates the development of cardio-vascular disease. Therefore we investigated the effects of testosterone replacement therapy (TRT) on endothelial function in hypogonadal men with type 2 diabetes.
Patients and methods: Thirty-three hypogonadal patients with type 2 diabetes, aged 35 years or older with testosterone levels below 8 nmol/l, were put on TRT (Nebido 1000 mg i.m). Before and seven months after TRT the parameters of metabolic control (HbA1c, lipids) and body composition using Dual energy X-ray absorptiometry (DXA) were measured. The endothelial function was assessed by measuring the endothelium-dependent flow-mediated vasodilation (FMD) of the brachial artery using a high resolution ultrasound. Patients filled out the AMS questionnaire before and after TRT.
Results: Serum testosterone levels increased from 6.6±1.7 to 8.6±2.1 nmol/l (P=0.000) after 7 months of TRT. FMD increased from 4.2±4.5% to 7.4±4.8%, (P=0.009). An increase in lean body mass from 73.9±9.5 to 74.9±9.5 kg (P=0.045) and a decrease in total body fat mass from 23.2±5.2 to 22.2±5.6 kg (P=0.006) was observed. There were no significant changes in lipid and HbA1c levels. The AMS score improved significantly.
Conclusions: Our trial was the first to examine the influence of TRT on the endothelial function in hypogonadal men with type 2 diabetes. TRT significantly improved endothelial function, body composition and symptoms of late-onset hypogonadism without influencing parameters of metabolic control. The beneficial effects of TRT on the endothelium might be testosterone mediated directly or indirectly via aromatisation to estradiol.