Testosterone Replacement Therapy Restores Normal Ghrelin in Hypogonadal Men

We recently described a connection between androgens and ghrelin in women affected by the polycystic ovary syndrome. To further investigate the interaction between sex steroids and ghrelin, we investigated circulating ghrelin levels in a group of hypogonadal men before and after therapeutic intervention aiming at normalization low testosterone (T) concentrations. Seven hypogonadal men were compared with nine overweight/moderately obese men matched for body mass index and body fat distribution parameters, as well as with 10 normal weight controls. Total and free T and plasma ghrelin levels were significantly lower in the hypogonadal men than in the control groups. Hypogonadal men also had a significantly higher insulin resistance state. Ghrelin levels were positively correlated with both total and free T concentrations. A significant correlation was also found between ghrelin and the anthropometric parameters and the insulin resistance indexes. However, in a multiple regression analysis in which a correction for all covariants was performed, only the relationship with total and free T persisted. After the 6-month replacement T therapy, ghrelin levels of hypogonadal patients increased and did not differ significantly in comparison with both control groups. The positive correlation between ghrelin and androgens still persisted after T replacement therapy, after adjusting for confounding variables. These data further indicate that sex hormones modulate circulating ghrelin concentrations in humans. This may be consistent with the concept that ghrelin may exert a relevant role in the endocrine network connecting the control of the reproductive system with the regulation of energy balance.