Women’s reproductive system as balanced estradiol and progesterone actions—a revolutionary, paradigm-shifting concept in women’s health

This review is to challenge current concepts of women’s reproduction with its cultural over-emphasis on estrogen and positive actions, while progesterone tends to be ignored or associated with negative effects. To explore the physiology, and the clinical implications of understanding that progesterone and estradiol interact in counterbalancing and complementary ways within a complex system that is Women’s Reproductive Health. Fundamental, descriptive, quantitative and experimental data all show that estradiol’s important cellular action is to promote growth and proliferation; by contrast, despite short-term proliferative effects, progesterone’s dominant actions are to inhibit proliferation, to enhance differentiation and promote maturation. Estradiol and progesterone variably interact in every cell and tissue in women’s bodies and across the life cycle. Since ovulation and thus progesterone’s presence is subclinical in normal-length cycles, we urgently need a convenient, home, once/cycle, inexpensive test of normal ovulation. Major funding is needed for ovulation-testing cycle-by-cycle over months or years in large population-based cohorts of adolescent, premenopausal and perimenopausal women. These women need to be followed for fertility and their later-life experiences of osteoporotic fracture, myocardial infarction, breast and endometrial cancers. In addition, all research with menstruating women participants and female mammals needs cycle-phase specific testing. It is difficult to perceive, much less to change, a current paradigm. With this journal issue, however, we have begun the important tasks of transforming concepts about women’s health, and setting the research agenda to advance the innovative understanding that women's reproductive and overall health becomes optimal when premenopausal menstrual cycle estradiol and progesterone actions are balanced within this complex system.