**6. Leptin in menstruation**

Hyperleptinemia may also be a determinant of menstrual function, again through its effects on the HPO axis [38]. It is well known that heavy exercise and decreased body fat (resulting in lower leptin levels) can lead to cessation of menses. Studies have demonstrated resumption of menses in women with hypothalamic amenorrhoea when treated with recombinant leptin [42, 43].

A cyclical variation has been observed in the serum leptin concentrations correlating with the phases of the menstrual cycle. In the early follicular phase, the concentration of leptin in serum is 14.9 ng/ml, which increases to 20.4 ng/ml in the mid-luteal phase [3]. Data have shown that a mid-cycle surge is seen in leptin levels corresponding to the mid-cycle LH surge. A recent study demonstrated that a 10% rise in leptin level throughout the menstrual cycle resulted in an increase in serum estradiol and luteal progesterone level [44].

The cyclicity of leptin levels in reproductive aged women in contrast to the constant levels in men and post-menopausal females further exemplify the role of leptin in regulation of menstrual cycle [44].
