HRT · Progestins
Progestin side effects: how synthetic progestogens compare to bioidentical progesterone.
Not all progestogens are the same. Synthetic progestins and bioidentical progesterone have different receptor profiles and different side-effect signatures. Here is a plain-language guide to what each one does, and does not, do.
The short answer
In modern menopause practice the biggest single decision on the progesterone side of HRT is which progestogen — because side effects vary meaningfully across the class. Bioidentical micronized progesterone generally has the most favorable side-effect and long-term safety profile; synthetic progestins vary based on their androgenic, glucocorticoid, and mineralocorticoid activity.
The most common progestin side effects
- Bloating and fluid retention — highest with medroxyprogesterone and norethindrone; drospirenone actually causes mild diuresis.
- Breast tenderness — usually 4–6 weeks; longer with continuous combined regimens.
- Mood changes — some women feel calmer, a minority feel low or irritable, especially with a PMDD history.
- Spotting or breakthrough bleeding — normal in the first 3–6 months of continuous combined HRT.
- Acne or oily skin — with androgenic progestins (norethindrone).
- Headaches — uncommon; often resolves with a route change (oral → vaginal for micronized progesterone).
- Sleepiness — specific to micronized progesterone; usually a benefit if dosed at bedtime.
Class-by-class comparison
- Medroxyprogesterone (Provera / Prempro): most bloating and mood effects; higher breast cancer signal in WHI at 5+ years.
- Norethindrone acetate (CombiPatch, Activella): androgenic — can cause acne but useful for heavy bleeding.
- Drospirenone (Angeliq): spironolactone-like — mild diuretic, can raise potassium.
- Levonorgestrel (Climara Pro, Mirena IUD): effective endometrial protection; local IUD delivery minimizes systemic exposure.
- Micronized progesterone (Prometrium): sedating at bedtime, mood-neutral for most, best breast-safety data among progestogens.
How to reduce side effects
- Take at bedtime with food.
- Try vaginal micronized progesterone (100 mg PV nightly) if oral causes sedation or low mood.
- Switch progestogens — if MPA is rough, micronized progesterone usually solves it.
- Consider a levonorgestrel IUD (Mirena) for local endometrial protection with minimal systemic effect.
- Give it 6–8 weeks before judging a new regimen.
Sources
- NAMS 2022 Hormone Therapy Position Statement
- E3N Cohort — progestogen-specific breast cancer risk
- WHI — long-term MPA + CEE safety data
Frequently asked questions
What are the most common progestin side effects?
Bloating, breast tenderness, mood swings, headaches, acne (with androgenic progestins), spotting or breakthrough bleeding in the first 3–6 months, and — for medroxyprogesterone specifically — a slight increase in breast cancer risk after 5+ years of combined HRT use.
Are progestin side effects the same as progesterone side effects?
No. "Progestin" refers to synthetic progestogens like medroxyprogesterone, norethindrone, and drospirenone. "Progesterone" (bioidentical, micronized) has a different metabolic profile — it is sedating, more mood-neutral, and has better breast safety data than synthetic progestins.
How long do progestin side effects last?
Bloating, breast tenderness, and mood effects usually settle within 6–8 weeks. Spotting on continuous combined HRT typically stops by month 6. Persistent side effects beyond that call for a dose or regimen change.
Can progestins cause depression?
A minority of women — often those with prior PMDD or postpartum depression — feel low mood or irritability on progestins. Switching to bioidentical micronized progesterone, or moving from oral to vaginal delivery, often resolves it.
Do progestins cause weight gain?
Some androgenic progestins (medroxyprogesterone, norethindrone) can cause modest fluid retention and appetite changes. Randomized data show most of the "weight gain" is fluid, not fat, and micronized progesterone shows no meaningful effect on body composition.
Which progestin has the fewest side effects?
For HRT, bioidentical micronized progesterone (Prometrium) generally has the most favorable side-effect profile: sedating at bedtime (a benefit for sleep), breast-safe in E3N data, and mood-neutral for most women.
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Medically reviewed by Kindr Health Clinical Team · Last reviewed 2026-06-19. Compounded medications are prepared by FDA-registered 503A pharmacies and are not FDA-approved drug products.