The role of leptin in female adolescence.

Leptin, the ob gene product, is related to the onset of puberty in animal models, but its role in human puberty is still rather undefined. In prepubertal girls and boys, leptin concentrations increase slowly with age and body-fat mass. In boys, this increase is interrupted in early puberty, when testosterone and lean body mass increase. In girls, leptin, along with the body-fat mass, continue to increase during puberty. Plasma leptin concentrations are significantly correlated with fat mass at all Tanner stages in males and females. The diurnal variation of leptin concentrations seen in adults is apparent for all age groups with no significant changes in the pattern across puberty. Leptin is bound in blood by a high-affinity binding protein identical with the soluble leptin receptor (sOB-R). In the first year of life, the concentration of sOB-R is high, and then a continuous decline of sOB-R follows until midpuberty. The therapeutic response to leptin treatment in a child with leptin deficiency confirms the importance of leptin in the regulation of body weight in humans, and establishes an important role for this hormone in the regulation of appetite. Still no evidence is available that would indicate leptin is a primary signal that initiates the onset of human puberty. Instead, it may act in a permissive way as one of several metabolic factors to allow pubertal maturation to proceed and later reproduction to occur.