Menstruation (mammal)
Menstruation in mammals is the shedding of the uterine lining (endometrium). It occurs on a regular basis in uninseminated sexually reproductive-age females of certain mammal species.
Leptin
In mice, and to a lesser extent in humans, leptin is required for male and female fertility. Ovulatory cycles in females are linked to energy balance (positive or negative depending on whether a female is losing or gaining weight) and energy flux (how much energy is consumed and expended) much more than energy status (fat levels). When energy balance is highly negative (meaning the woman is starving) or energy flux is very high (meaning the woman is exercising at extreme levels, but still consuming enough calories), the ovarian cycle stops and females stop menstruating. Only if a female has an extremely low body fat percentage does energy status affect menstruation. Leptin levels outside an ideal range may have a negative effect on egg quality and outcome during "in vitro" fertilization. Leptin is involved in reproduction by stimulating gonadotropin-releasing hormone from the hypothalamus.