Circulating leptin levels have been measured over development in several species. In female mice, a peak in plasma levels of leptin during the second week of postnatal life has been reported, which occurs independently of changes in body weight and before the developmental increase in estradiol. Gruaz et al. examined plasma leptin levels in female rats between postnatal Days 24 and 59 (average age of VO approximately Day 40) and observed a steady rise in leptin levels in proportion to body weight over the sampling period, although one cannot discount the possibility of a peak occurring before Day 24. Studies in male rhesus macaques show little change in leptin levels over the peripubertal period, when LH, FSH, and testosterone levels begin to climb to adult levels. buy yasmin online
In the human, as in the mouse, there is an absolute requirement of leptin to initiate human pubertal development, as evidenced by the fact that individuals with mutations in the leptin gene are hypogonadal and infertile. Leptin levels in girls tend to increase steadily over the period of sexual development, while in boys there is a peak in leptin levels around Tanner stage 2 accompanied by a gradual decline throughout the remainder of puberty.