Hypogonadotropic Hypogonadism in Erectile Dysfunction Associated with Type 2 Diabetes Mellitus: A Common Defect?

The objective of this study was to evaluate the gonadal function in men with type 2 diabetes with erectile dysfunction. Methods: We examine records of 50 patients with type 2 diabetes and erectile dysfunction who had low free testosterone concentrations. All patients had plasma concentrations of luteinizing hormones (LH), follicle-stimulating hormone (FSH), and prolactin measured. Results: Of the 50 patients with low free testosterone concentrations (0.97 ± 0.4 ng/dL; reference range, 1.30-3.10), 43 had normal (inappropriately low) LH (5.9 ± 2.9 mIU/mL), FSH (5.6 ± 2.4 mIU/mL), and testosterone concentrations, five had elevated LH, FSH concentrations (Hypogonadotropic hypogonadism), and two had prolactinoma. Patients with hypogonadotropic hypogonadism were in their mid 50's and had experienced a decline in their testosterone levels much earlier than that expected from the normal age-related decline. Although a majority of the patients were obese, there was no relationship between testosterone (free or total) and BMI, between testosterone and HbA_1c, duration of diabetes or the age of the patient. Patients given testosterone supplementation experienced a subjective improvement in their wellbeing, but reported no significant improvement in their erectile dysfunction. Conclusion: We conclude that patients with erectile dysfunction require careful assessment and that the most frequent gonadal defect in these patients is that of hypogonadotropic hypogonadism, a defect not previously associated with type 2 diabetes. The mechanism underlying this defect requires investigation. The value of testosterone replacement in such patients needs to be assessed critically.