Testosterone Raises Insulin Sensitivity – Men’s Health

Testosterone Raises Insulin Sensitivity –  Men’s Health

Testosterone Raises Insulin Sensitivity

Giving testosterone to men with type 2 diabetes who are deficient in the hormone improved their insulin sensitivity, reports researchers from the University of Buffalo (New York, USA).  Paresh Dandona and colleagues conducted a randomized controlled trial of 81 men with type 2 diabetes.  Men were randomized to treatment with testosterone or placebo for 6 months. At baseline, those with hypogonadism had a higher body mass index (BMI) and a higher fat mass than those who didn’t have low testosterone.  The team found that hypogonadal men with type 2 diabetes had significantly lower insulin sensitivity than those who did not have hypogonadism; further, that association remained even when controlling for weight and age (P=0.017). As well, free testosterone rose dramatically (4.1 nmol/L to 12.4 nmol/L), while placebo subjects had no significant changes in this parameter. Commenting that there was a “dramatic” 25% increase in insulin sensitivity … after these men took testosterone for 6 months,” the study authors note total lean body mass increased significantly for testosterone patients while fat mass significantly diminished in this group.

OBJECTIVE— The goal of this study was to examine the relationship between serum testosterone levels and insulin sensitivity and mitochondrial function in men.

RESEARCH DESIGN AND METHODS—A total of 60 men (mean age 60.5 ± 1.2 years) had a detailed hormonal and metabolic evaluation. Insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. Mitochondrial function was assessed by measuring maximal aerobic capacity (Vo2max) and expression of oxidative phosphorylation genes in skeletal muscle.

RESULTS—A total of 45% of subjects had normal glucose tolerance, 20% had impaired glucose tolerance, and 35% had type 2 diabetes. Testosterone levels were positively correlated with insulin sensitivity (r = 0.4, P < 0.005). Subjects with hypogonadal testosterone levels (n = 10) had a BMI >25 kg/m2 and a threefold higher prevalence of the metabolic syndrome than their eugonadal counterparts (n = 50); this relationship held true after adjusting for age and sex hormone–binding globulin but not BMI. Testosterone levels also correlated with Vo2max (r = 0.43, P < 0.05) and oxidative phosphorylation gene expression (r = 0.57, P < 0.0001).

CONCLUSIONS—These data indicate that low serum testosterone levels are associated with an adverse metabolic profile and suggest a novel unifying mechanism for the previously independent observations that low testosterone levels and impaired mitochondrial function promote insulin resistance in men.