Progesterone
Status
FDA-approved. FDA-approved labeling exists as Prometrium for prevention of endometrial hyperplasia in postmenopausal women receiving oestrogen, and for secondary amenorrhoea. It carries the oestrogen-plus-progestin class boxed warning covering cardiovascular disorders, breast cancer and probable dementia, and is contraindicated in peanut allergy.
What it is
A hormone used in prescribed therapy alongside estrogen, often at night.
What published research measured
Micronized progesterone, structurally identical to the endogenous hormone, distinct from the synthetic progestins in both receptor behaviour and clinical data. Its established role is endometrial protection in women taking oestrogen, where randomized evidence supports prevention of endometrial hyperplasia. The comparison that matters is with medroxyprogesterone acetate, the progestin used in the Women's Health Initiative combined arm: observational cohorts including the large French E3N study have reported a more favourable breast cancer signal for micronized progesterone, though this has not been settled by randomized data. Oral administration produces sedating metabolites through hepatic first pass, which is why it is usually taken at night and why drowsiness is a common reported effect. It is prepared in peanut oil in the standard capsule.
Source
E3N cohort study on progestogen type and breast cancer risk · FDA labeling for Prometrium
Sources
No linked primary source is on file for this entry yet.
Educational use only, never medical advice. No doses.