Influence of Male Hormones on Regional Fat Metabolism

The male sex hormone, testosterone, plays an important role in determining body fat distribution in men. This is especially evident in the dramatic shift in body composition as boys and girls reach sexual maturity. Normal weight women have twice the body fat of a normal weight man (30% vs. 15% on average) and men will have twice the stomach fat as women (10% vs. 5% of fat as intra-abdominal, men vs. women). These are likely sex-steroid linked events. Short and long term changes in regional fat distribution accompany testosterone deficiency and can be reversed by testosterone replacement. Testosterone deficient men have increased stomach fat that can be reversed with testosterone replacement therapy. Interestingly, the mechanism by which testosterone affects where we store fat is unknown. It is important to understand how testosterone influences where we store fat as it is well established that increased stomach fat results in elevated disease risk. The proposed study aims to examine the effect of short term, temporary testosterone decreases on how and where men store fat. The investigators will compare fat storage between men given Lupron to temporarily decrease testosterone levels those that receive Lupron plus testosterone replacement vs. a no treatment control group. Comparing these three groups will allow us to understand the effects of testosterone on short-term changes in fat tissue function that lead to the long-term changes in where we store body fat.