Regulating menstrual bleeding. A prime function of progesterone.

Progesterone plays a crucial role in the coordination of endometrial breakdown as well as in the determination and regulation of menstrual blood loss and endometrial transudation of fluid. Furthermore, long-term exposure of the endometrium to progesterone can result in abnormal angiogenesis. Although additional investigations of the estrogen-progesterone relationship are needed, the relative concentrations of these two hormones appear to have important effects on bleeding patterns. Current research is aimed at greater understanding of the ways in which these two hormones interact with several complex cellular and metabolic mechanisms to regulate endometrial bleeding.