The role of leptin in regulating neuroendocrine function in humans

Eating disorders are a group of disease states including anorexia nervosa, bulimia nervosa and binge eating on one end as well as episodic or chronic overeating resulting in obesity at the other end of the spectrum. These disorders are characterized by decreased and/or increased energy intake and are frequently associated with hormonal and metabolic disorders. The discovery of leptin, an adipocyte-secreted hormone acting in the brain to regulate energy homeostasis, and its subsequent study in human physiology have significantly advanced our understanding of normal human physiology and have provided new opportunities for understanding and possibly treating disease states, such as anorexia and bulimia nervosa. It has been recently discovered that leptin levels above a certain threshold are required to activate the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-thyroid axes in men, whereas the hypothalamic-pituitary-adrenal, renin-aldosterone, and growth hormone-IGF-1 axes may be largely independent of circulating leptin levels in humans. In this review, we summarize the latest findings related to the role of leptin in the regulation of several neuroendocrine axes, such as the hypothalamic-pituitary-gonadal and the hypothalamic-pituitary-thyroid axes in humans and discuss its potential pathophysiologic role in eating disorders.