Glossary · Treatments

Medroxyprogesterone acetate (Provera)

Also called: MPA, Provera.

Definition: Medroxyprogesterone acetate (MPA) is the synthetic progestin used in the WHI estrogen-plus-progestin arm. It is effective for endometrial protection but has been associated in observational and randomized data with a higher breast cancer signal than bioidentical micronized progesterone, leading many modern HRT practices to prefer micronized progesterone.

Detailed definition

Medroxyprogesterone acetate (MPA), branded as Provera and the progestin component of Prempro, is a synthetic 17α-hydroxyprogesterone derivative. It binds progesterone receptors with high affinity and is effective at protecting the endometrium from estrogen-driven hyperplasia. MPA was the progestin in the WHI estrogen-plus-progestin arm that drove the headline 2002 breast cancer signal; subsequent observational data (notably the E3N study) and pooled analyses suggest the breast cancer signal seen in WHI was specific to MPA and is substantially smaller or absent with bioidentical micronized progesterone. MPA is also used as injectable contraception (Depo-Provera, 150 mg IM every 3 months).

Why it matters in menopause

Many women associate "the WHI HRT" with all hormone therapy and avoid HRT entirely. The reality is narrower: the WHI breast cancer signal came from a specific synthetic progestin (MPA) in older oral conjugated equine estrogens in older women. Modern HRT with transdermal estradiol plus bioidentical micronized progesterone has a different (and much more favorable) safety profile for healthy women in the timing window.

Sources

External references: Wikipedia.

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