The relationship between metabolism and reproduction remains a mystery in female endocrinology. Such substances as insulin, amino acids and IGFBP-I have been proposed as signals of body mass fat on the genital axis. Today this role is claimed by leptin, a protein hormone decoded from the obesity gene and is secreted exclusively from adipose tissue. This hormone acts on the central nervous system (CNS) to result in the suppression of food intake and increase in energy consumption. What is more, it also influences the capacity for reproduction. This paper reports findings with regard to the factors influencing the secretion of leptin and identification of the leptin's hormonal receptors. Particular emphasis was placed on the relationship between secretion of leptin and disturbances in menstruation, the anticipated role of this hormone in the pathogenesis of the polycystic ovarian syndrome (PCOS) and its effects on the reproductive capacity.