Dhindsa S et al. (2004) Frequent occurrence of hypogonadotropic hypogonadism in type 2 diabetes. J Clin Endocrinol Metab 89: 5462–5468

Several studies have shown that men with type 2 diabetes tend to have lower total testosterone levels than nondiabetic men of similar age and body mass index (BMI). Dhindsa et al. have recently investigated the prevalence and etiology of hypogonadism in these patients.

The single-center study was based on fasting blood samples from 103 consecutive male patients with type 2 diabetes. Measurement of free testosterone levels, using two different methods, revealed that 33% of patients were hypogonadal. These patients also had lower levels of luteinizing hormone and follicle-stimulating hormone than those whose free testosterone levels were in the normal range. In addition, an inverse correlation was shown between free testosterone levels and BMI, although obesity did not account for all cases of hypogonadism.

In conclusion, the study shows that hypogonadism is common in men with type 2 diabetes, and that it is secondary to a hypogonadotropic defect. Further studies will be needed to understand the etiology of the defect and to consider whether testosterone replacement therapy might be appropriate in such patients. The authors warn against making a diagnosis of hypogonadism in type 2 diabetes patients on the basis of total testosterone levels alone, since this would have led to 12% false negatives and 36% false positives in their study. They recommend, therefore, that patients with low or low normal total testosterone should undergo assessment of free testosterone levels before a diagnosis is made.