Progesterone is a steroid hormone crucial to the female reproductive system. Its use to support reproductive and hormonal health, particularly in the context of the menstrual cycle, pregnancy maintenance, and hormone replacement therapy (HRT), is strongly backed by scientific evidence. Progesterone is naturally produced by the ovaries after ovulation and is essential for preparing the endometrium (uterine lining) for implantation of a fertilized egg, as well as maintaining pregnancy. In cases of luteal phase deficiency or infertility, supplementation with progesterone has been shown to improve outcomes by supporting endometrial receptivity. Progesterone is also used to prevent preterm birth in women with a history of spontaneous preterm delivery, with clinical trials (such as the 2011 Meis study in the New England Journal of Medicine) demonstrating significant reductions in risk.

In hormone replacement therapy, progesterone is often combined with estrogen in women with intact uteri to prevent endometrial hyperplasia and reduce the risk of endometrial cancer. The use of micronized progesterone, which mimics the natural hormone, is considered safer and well tolerated compared to synthetic progestins. The efficacy and safety of progesterone for these indications are supported by numerous randomized controlled trials and are reflected in clinical guidelines from authoritative bodies such as the American College of Obstetricians and Gynecologists (ACOG) and the Endocrine Society.