Ghrelin is a recently described hormone secreted by the stomach. Ghrelin 
administration in ad-libitum-fed rodents was shown to increase appetite as well 
as body weight and body fat content, showing metabolic effects of ghrelin in 
vivo and suggesting its involvement in the pathogenesis of obesity. However, 
plasma ghrelin concentration was shown to be inversely correlated with body 
weight and body fat in people and rodents. Increased plasma ghrelin 
concentration was also reported during diet-induced weight loss and in 
malnourished states. These findings suggest that circulating ghrelin is 
regulated by nutritional state and body fat with a feedback mechanism opposing 
changes in body composition, with a potential key adaptive role during calorie 
restriction. Plasma ghrelin concentration was shown to be increased in advanced 
renal failure and hemodialysis patients. The known metabolic effects of ghrelin 
and the potential implications of hyperghrelinemia in kidney disease will be 
discussed in this article.