The impact of micronized progesterone on the endometrium: a systematic review.

Postmenopausal women with an intact uterus using estrogen therapy should receive a progestogen for endometrial protection. International guidelines on menopausal hormone therapy (MHT) do not specify on progestogen type, dosage, route of application and duration of safe use. At the same time, the debate on bioidentical hormones including micronized progesterone increases. Based on a systematic literature review on micronized progesterone for endometrial protection, an international expert panel's recommendations on MHT containing micronized progesterone are as follows: (1) oral micronized progesterone provides endometrial protection if applied sequentially for 12-14 days/month at 200 mg/day for up to 5 years; (2) vaginal micronized progesterone may provide endometrial protection if applied sequentially for at least 10 days/month at 4% (45 mg/day) or every other day at 100 mg/day for up to 3-5 years (off-label use); (3) transdermal micronized progesterone does not provide endometrial protection.