Leptin in relation to growth and developmental processes in the fetus.

Leptin, a 16-kilodalton protein secreted by the adipose tissue in proportion to the amount of energy stored in adipose tissue, conveys to the hypothalamus information on energy homeostasis and regulates reproductive function. In addition, there is accumulating evidence that leptin produced by placental or fetal tissues acts through specific leptin receptors to regulate fetal growth and development. Although leptin levels are correlated with insulin and insulin-like growth factor (IGF)-1 levels, observational studies in humans indicate that its effects on fetal growth are independent of these axes and of adiposity. The extent to which leptin per se mediates the fetal growth and developmental abnormalities associated with disease states such as diabetes, hypoxia, or preeclampsia remains to be fully clarified by future studies in humans. It is hoped that clarification of these mechanisms may provide novel therapeutic approaches.