Contrasting Testosterone Concentrations in Type 1 and Type 2 Diabetes

We have recently reported (1) that male patients with type 2 diabetes have frequent hypogonadotrophic hypogonadism. We have now asked whether a similar defect may be observed in type 1 diabetic males to determine whether diabetes per se is the cause of hypogonadotrophic hypogonadism. Fifty patients with type 1 diabetes (age range 23–58 years) and 50 age-matched patients with type 2 diabetes (age range 28–51 years) were included in the study. Patients with known history of hypogonadism, panhypopituitarism, or chronic debilitating disease such as renal failure, cirrhosis, or HIV infection were excluded from the study. Fasting blood samples were obtained from the patients, and total testosterone (TT), free testosterone (FT), sex hormone–binding globulin (SHBG), leutinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured as previously described (1). FT and bioavailable testosterone (bioT) were calculated from SHBG and TT as previously described (1). Hypogonadism was defined as low FT or low calculated FT (2). Mann-Whitney rank-sum test or Student’s t test for unpaired data, χ2 test, and Spearman’s test were used as appropriate (Sigmastat software). The mean TT, FT, calculated FT, and bioT concentrations in type 1 diabetic patients were in the middle of the normal range (Table 1). No patient had subnormal TT concentrations; three patients had supranormal TT, while two patients had subnormal FT and bioT concentrations. The mean TT concentration in patients with type 2 diabetes was significantly lower than that in type 1 diabetic subjects …