Bioidentical progesterone
Bioidentical progesterone is identical to the body's own progesterone, available as FDA-approved Prometrium or compounded products for menopause HRT.
How it works
The term 'bioidentical progesterone' refers to progesterone with the same molecular structure as the hormone produced by the human ovaries, in contrast to synthetic progestins (like medroxyprogesterone or norethindrone), which have different structures and different receptor binding profiles. FDA-approved bioidentical progesterone is sold as Prometrium (oral micronized capsules). Compounded bioidentical progesterone is made by specialty pharmacies and can be formulated in various concentrations and delivery forms, but without FDA oversight of potency or purity. For uterine protection in combination hormone therapy, FDA-approved Prometrium is the evidence-based choice — the NAMS position statement explicitly recommends against compounded hormone preparations as a first choice.
The clinically important distinction between bioidentical progesterone and synthetic progestins is the neurosteroid effect: bioidentical progesterone metabolizes into allopregnanolone, which acts on brain GABA-A receptors to produce sedation and calming. This is why bioidentical progesterone is associated with sleep improvement — an effect not shared by medroxyprogesterone or norethindrone. For people choosing between bioidentical progesterone and a synthetic progestin, this difference is clinically meaningful for sleep.
How to track Bioidentical progesterone
- Sleep quality — the GABA-A neurosteroid effect of bioidentical progesterone is distinctive; tracking sleep quantifies whether you are getting this benefit.
- Dosing form and timing — FDA-approved vs. compounded, oral vs. other forms; the formulation affects both efficacy and what tracking data means.
- Mood and anxiety — GABA-A modulation affects both, and some people report improved calm with bioidentical progesterone vs. mood changes with synthetic progestins.
- Side effects: dizziness, next-day grogginess, breast tenderness, bloating.
- Breakthrough bleeding or spotting — especially important on cyclic regimens.
- If using FDA-approved Prometrium, track the specific lot if your pharmacy dispenses from multiple suppliers — standardized potency means less batch variability than compounded products.
- Log the exact time you use progesterone each evening — the timing-dependence of the sedating effect means your log will show whether consistency of timing affects sleep quality.
- Rate sleep quality with a consistent scale each morning — it is the most concrete way to evaluate whether the neurosteroid effect is contributing.
- If you switched from a synthetic progestin to bioidentical progesterone, treat the switch date as a new baseline and track sleep and mood in the weeks following.
- Log breakthrough bleeding with dates and description — it is one of the most diagnostically important data points in hormone therapy.
Questions to ask your physician
- My sleep quality log since starting bioidentical progesterone shows [pattern]. Is that the sedating effect working as expected at my dose?
- I switched from [synthetic progestin] to bioidentical progesterone on [date]. My mood log shows [pattern] in the weeks since. Is that consistent with the different receptor profile?
- I've been logging breakthrough bleeding on [dates, description] — what does that pattern suggest about my regimen?
- I'm using a compounded progesterone product. Given NAMS guidance recommending FDA-approved forms, should we discuss switching to Prometrium?