HRT · Progestogens
Micronized progesterone vs synthetic progestins
Every woman with a uterus on estrogen needs a progestogen to protect the endometrium. But bioidentical micronized progesterone and synthetic progestins are chemically and clinically distinct. The distinction matters for breast, mood, and cardiovascular outcomes.
Options for endometrial protection
- Micronized progesterone 100–200mg oral at bedtime
- Vaginal micronized progesterone (avoids sedation)
- Levonorgestrel IUD (Mirena)
- Synthetic progestins (MPA, norethindrone) — historical, largely superseded
Frequently asked questions
Are they interchangeable?
No. Micronized progesterone is molecularly identical to what the ovary makes; synthetic progestins are not.
Does progesterone cause breast cancer?
The E3N cohort found no increased breast cancer risk with estradiol + micronized progesterone for up to 5 years, unlike synthetic combinations.
Which is better for sleep?
Oral micronized progesterone at bedtime has mild sedative effects due to allopregnanolone metabolites.
Is a Mirena IUD acceptable?
Yes — off-label but widely used for endometrial protection with excellent local delivery and minimal systemic exposure.
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Written and medically reviewed by the Kindr Health Clinical Team · Published 2026-06-19 · Last reviewed 2026-07-01. Compounded medications are prepared by FDA-registered 503A pharmacies and are not FDA-approved drug products.