Testosterone Plasma Concentration is Associated with Insulin Resistance in Male Hypertensive Patients

Background: Low testosterone levels are a common finding among men with Type 2 Diabetes Mellitus (T2DM) and are inversely related to insulin resistance. Whether this relationship holds true in patients with hypertension, but normal glucose tolerance or prediabetes, is unclear. Methods: We recruited 87 male outpatients with essential arterial hypertension, aged 35-70 years. Anthropometric data were collected, an Oral Glucose Tolerance Test (OGTT) performed, and the homeostasis model assessment of insulin resistance (HOMA-IR) score calculated. Follicle-Stimulating Hormone, Luteinizing Hormone, testosterone, Sex Hormone-Binding-Globulin and free-testosterone were measured. The concentrations of sex hormones were compared between normoglucotolerant, prediabetic and diabetic patients. Non-parametric tests were applied as appropriate to verify differences among groups, while multiple linear regression was used to predict the variability of testosterone and free-testosterone. Results: Total serum testosterone concentration was significantly lower in T2DM in comparison to normoglucotolerant subjects (p<0.01) and was inversely related to body mass index (r=- 0.25, p<0.01), waist circumference (r=- 0.27, p<0.01), pre and post-OGTT plasma glucose (r=- 0.4, p<0.0001 and r=- 0.29, p<0.01, respectively), pre and post-OGTT plasma insulin (r=- 0.42, p<0.0001 and r=- 0.42, p<0.0001) and HOMA-IR (r=- 0.46, p<0.0001). Similar associations were observed for free testosterone; HOMA-IR was related to testosterone and free-testosterone even in patients with normal glucose tolerance (r=- 0.47, p<0.01 and r=- 0.34, p<0.05, respectively). At multivariate analysis HOMA-IR was the only variable associated to testosterone (p<0.001) and free-testosterone (p<0.05) plasma concentration. Conclusions: In males with hypertension, the link between insulin sensitivity and hypothalamic-pituitary-gonadal axis is maintained along the entire spectrum of glucose tolerance.