Leptin in reproduction

In mammals, the function of the reproductive system is dependent on the ava ilability of energy in the environment. It is well established that acute m odifications of energy balance modulate the hypothalamic-pituitary-gonadal axis. In several species, fasting and caloric restriction have been shown t o cause the suppression of pulsatile luteinizing hormone secretion,via an i nhibition of the gonadotropin-releasing hormone pulse generator. Such a mec hanism probably prevents energy being wasted for reproduction. By contrast, excessive energy storage a nd obesity interfere with the correct regulatio n of the reproductive axis. The identification of leptin and leptin recepto rs, along with studies performed in animal models of leptin deficiency and resistance, has focused attention on the role of this molecule in reproduct ion, and disclosed new aspects of the relationship between energy stores, a dipose tissue a nd reproductive function, Here, we discuss the central and peripheral effects of leptin on reproductive tissues, and try to fit a comp lex reality into a simplified model. In particular,the roles of leptin in r eproduction at different anatomical levels and in various clinical and expe rimental settings are discussed.