Low testosterone and insulin resistance in hypertension-prone men

The aim of the study was to elucidate the relationship between peripheral insulin sensitivity and testosterone and sex hormone binding globulin (SHBG) in the development of hypertension. An euglycaemic hyperinsulinaemic clamp was performed to determine insulin sensitivity and sex steroid hormones and SHBG were analysed in 35 normotensive men with a family history of hypertension (relatives) and 27 age and body mass index matched controls (controls). Relatives had lower concentrations of serum total testosterone and SHBG, and lower insulin sensitivity compared to controls. Free testosterone concentrations were the same in both groups. Relatives had lower maximal oxygen uptake compared to controls. Total testosterone and SHBG were correlated to basal insulin concentration and insulin sensitivity in relatives, but not in controls. In stepwise regression analysis, total testosterone explained 37% and walst circumference 6% of the variation of insulin sensitivity in relatives, and walst circumference explained 29% in controls. When substituting testosterone with SHBG in this model, SHBG explained 48% of the variation in insulin sensitivity in relatives. The finding of a closer relationship between insulin sensitivity and SHBG than between insulin sensitivity and total testosterone suggests that the SHBG level is primarily influenced by insulin sensitivity in the relatives.