Glossary · Treatments

Progestin

Definition: Progestins are synthetic progesterone-like molecules — including medroxyprogesterone acetate, norethindrone, drospirenone, and levonorgestrel — used for endometrial protection in HRT and as the progestogen component in hormonal contraception. They are not bioidentical to progesterone and have varying side effect and safety profiles.

Detailed definition

Progestins are synthetic compounds that bind the progesterone receptor and produce progestational effects. They are structurally related to progesterone but differ in pharmacology — most progestins also have varying degrees of androgenic, estrogenic, antiandrogenic, or glucocorticoid activity. Common progestins in HRT include: medroxyprogesterone acetate (Provera), norethindrone (norethisterone), drospirenone, and levonorgestrel. The 52-mg levonorgestrel-releasing IUD (Mirena) provides endometrial protection in women on estrogen with a uterus and is a particularly well-tolerated option for women who do not want a daily progestogen. Observational data — including the French E3N study — suggest that synthetic progestins (notably medroxyprogesterone) carry a higher breast cancer signal than bioidentical micronized progesterone over 5+ years of use, contributing to the modern preference for micronized progesterone in HRT.

Why it matters in menopause

For women with a uterus on systemic estrogen, the choice of progestogen matters. Bioidentical micronized progesterone is generally preferred. Synthetic progestins remain useful in specific contexts (combined patches, IUDs, women who tolerate a particular progestin well).

Sources

External references: Wikipedia.

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