What Is the Difference?
All HRT containing a progestogen includes it for one reason: to protect the uterine lining (endometrium) from the proliferative effect of oestrogen unopposed. Without progestogen, oestrogen-only HRT is associated with endometrial cancer — it cannot be used by women who still have a uterus. The difference lies in what type of progestogen is used. Synthetic progestins (medroxyprogesterone acetate, norethisterone, levonorgestrel) are chemically modified compounds that bind progesterone receptors but have slightly different and sometimes less favourable effects on other tissues. Micronised progesterone (branded as Utrogestan in the UK and EU) is chemically identical to the progesterone the ovaries produce.
The Breast Cancer Difference
The most clinically significant difference between progestogen types is their apparent effect on breast tissue. The E3N French cohort study (80,000 women) found that combined HRT with synthetic progestins was associated with significantly higher breast cancer risk than HRT using micronised progesterone, which showed little to no increased risk compared to oestrogen-only HRT. The mechanism is thought to relate to progestins' androgenic activity and differing effects on breast cell proliferation. The British Menopause Society and NICE updated guidelines recommend micronised progesterone as the preferred progestogen in systemic HRT for most women.
The Sleep, Mood, and Anxiety Advantage
Micronised progesterone has a direct anxiolytic (anxiety-reducing) and sleep-promoting effect: it is metabolised to a neurosteroid called allopregnanolone, which acts on GABA-A receptors in the brain — the same receptors targeted by benzodiazepines and sleep medications. Many women on micronised progesterone report improved sleep quality and reduced anxiety within weeks of starting. Synthetic progestins, particularly medroxyprogesterone acetate, do not share this neurosteroid metabolite and are associated with worsened mood and sleep in some women.
How It Is Taken
Micronised progesterone (Utrogestan) is typically taken orally at night (100–200mg depending on regimen) or as a vaginal pessary. Taking it orally at bedtime maximises the sleep-promoting effects and reduces daytime drowsiness from the allopregnanolone metabolite. A Mirena IUD (levonorgestrel, a synthetic progestin, but acting predominantly locally in the uterus with minimal systemic absorption) is another option for endometrial protection, though it does not offer the systemic benefits of body-identical progesterone. If you are currently on HRT with a synthetic progestin and experiencing mood, sleep, or breast concerns, ask your doctor whether switching to micronised progesterone is appropriate for you.
Medical Disclaimer
This article is written for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making health decisions.
Dr. Lisa Park
MD, FACOG
All TryHerCare articles are written and reviewed by qualified medical professionals. Our content is clinician-reviewed to ensure accuracy and clinical relevance.
