Weight loss increases circulating levels of ghrelin in human obesity

Objective Ghrelin, a novel endogenous ligand for the GH secretagogue receptor, has been reported to have adipogenic actions and induce weight gain in addition to its GH-releasing properties. Interestingly, recent data indicate that ghrelin is downregulated in human obesity, which is also known to be accompanied by reduced GH levels. Patients and Methods To investigate the influence of weight loss on circulating levels of ghrelin we recruited eight obese women among patients attending a 6-month weight-loss course organized by The Danish Heart Association. We measured body composition including computerized tomography as well as fasting plasma ghrelin concentrations before and after weight loss. Results Plasma ghrelin concentrations increased by 12% following weight loss (P<0.01), and the increase in ghrelin levels was positively correlated with the extent of weight loss (r=0.68, P<0.05). Exposure to exogenous GH intravenously did not influence fasting ghrelin levels either before or after weight loss. Our data further suggest the existence of hyperghrelinaemia in a single subject with long-standing obesity but no signs of GH excess. Conclusions This study provides evidence of a reversible suppression of ghrelin associated with obesity. The feasibility of measuring ghrelin in the circulation provides a new tool for the investigation of the complex hormonal regulation of appetite and energy balance.