Endocrine Abstracts

Type 2 diabetes mellitus is associated with increased incidence of low serum testosterone levels in men. Testosterone is known to be positively correlated with insulin sensitivity. Rosiglitazone is an insulin sensitizing agent that reduces insulin resistance by binding to PPAR gamma receptor. The purpose of this study was to determine the effect of Rosiglitazone on testosterone levels in hypogonadal men with Type 2 diabetes.

This study was approved by BDGH ethics committee. 16 male patients, above the age of 30, with Type 2 diabetes and hypogonadism, registered with the diabetes centre at BDGH were recruited. Hypogonadism was defined as total testosterone <12nanomoles per litre. 4 patients had primary gonadal failure and 12 patients had mixed primary and secondary gonadal failure. Patients with elevated CRP [>10milligrames per litre] were excluded. Baseline bloods were taken between 8 and 10am and analysed for levels of total testosterone, SHBG and HbA1C. Bloods were taken on two separate days and a mean of the two levels were taken. Bioavailable testosterone was calculated using the mathematical formula (1). Patients were then commenced on Rosiglitazone 8mg a day and the blood tests were repeated at 2 and 4 months.

Glycaemic control significantly improved after 4 months with Rosiglitazone treatment [Mean HbA1C 8.27% vs 6.9%]. Total testosterone levels increased after 4 months [Mean TT 10.07 vs 12.97nanomoles per litre, p=0.0046]. SHBG levels increased as well [Mean 27.06 vs 33.64 nanomoles per litre, p=0.06]. Bioavailable testosterone levels also improved after 4 months [Mean BT 3.44 vs 4.15nanomoles per litre, p=0.012].

This study shows that Rosiglitazone increases testosterone levels in hypogonadal men with Type 2 diabetes. However it is unclear whether this effect occurs as a result of reduction in insulin resistance or a consequence of improved glycaemic control.

(1) Morris et al. European Journal of Endocrinology 2004; 151: 241-250