Long-term testosterone administration increases visceral fat in female to male transsexuals.

The amount of intraabdominal (visceral) fat is an important determinant of disturbances in lipid and glucose metabolism. Cross-sectional studies in women have found associations between high androgen levels and visceral fat accumulation. The causal relation between these phenomena is unknown. We, therefore, studied prospectively the effect of testosterone administration on body fat distribution in 10 young, nonobese, female to male transsexuals undergoing sex reassignment. Before, after 1 yr, and after 3 yr of testosterone administration, magnetic resonance images were obtained at the level of the abdomen, hip, and thigh to quantify both sc and visceral fat depots. After 1 yr of testosterone administration, sc fat depots at all levels showed significant reductions compared to baseline measurements. The mean visceral fat area did not change significantly, but subjects who gained weight in the first year after testosterone administration showed an increase in visceral fat. After 3 yr of testosterone administration, sc fat depots were no longer significantly lower compared to pretreatment measurements, but the mean visceral fat depot had increased significantly by 13 cm2 (95% confidence interval, 4-22 cm2), a relative increase of 47% (95% confidence interval, 8-91%) from baseline. The increase in visceral fat was most pronounced in those subjects who had gained weight. We conclude that long term testosterone administration in young, nonobese, female subjects increases the amount of visceral fat. In addition, an increase in weight in this hyperandrogenic state leads to a preferential storage of fat in the visceral depot.