Leptin in human reproduction

The recent discovery of the obese (ob) gene has provided new insight into the mechanism which controls body fat mass. Leptin, a product of the ob gene, serves as the link between fat and the brain. This protein, by acting at the level of the hypothalamus, decreases food intake and increases energy expenditure. Animals that lack leptin (ob/ob mice) develop profound obesity and become infertile. Treatment of these animals with leptin reduces food intake and restores normal fertility. Although leptin is important for the control of fat stores in certain species, the role of this substance in the development of human obesity remains obscure. However, it has been speculated that, in humans, obesity is related to leptin resistance. The relationship between fat and reproduction has been recognized for >20 years. This article discusses the relationship between leptin and human reproduction. In particular, recent knowledge about the possible role of leptin in various conditions such as puberty, polycystic ovary syndrome and pregnancy is reviewed. Also, the article discusses the possible role of leptin in ovarian function and the relationship of this protein with gonadal steroids. It is expected that future research will clarify the physiological importance of leptin in human reproductive function.