Progesterone
Also called P4
Progesterone is a hormone made mainly by the ovaries that prepares the endometrium, the lining of the uterus, for a possible pregnancy each month. If no pregnancy occurs, the lining sheds as a menstrual period; if one does, progesterone rises to support it. Together with estrogen, it controls the menstrual cycle.
Progesterone is not the same as a progestin. A progestin is a lab-made compound that acts like progesterone, and some sources use "progestin" for every hormone that acts like progesterone, synthetic or not.
Why it matters after 45
Progesterone levels decline in the years leading up to menopause, as ovulation becomes irregular and then stops. The term comes up again in menopausal hormone therapy: people who still have a uterus and take estrogen usually also need a progestin, because estrogen taken alone raises the risk of uterine cancer.
Where it comes up
References
- Cleveland Clinic. Progesterone. https://my.clevelandclinic.org/health/body/24562-progesterone
- MedlinePlus. Progesterone Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/progesterone-test/
- Cleveland Clinic. Hormone Therapy for Menopause. https://my.clevelandclinic.org/health/treatments/15245-hormone-therapy-for-menopause-symptoms
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms