The Skinny on Progesterone

October 26, 2018



  • Improved deep sleep.  The sleep architecture with progesterone was more natural than with zolpidem (Ambien).  Anyone who knows me or who plans to read this blog will know how much I am obsessed with sleep.  It's a basic building block for health.  We need sleep to maintain our weight, metabolism, brain function, mood, immune system - on and on.  We must have it.   (References:  PMID 29649764, 29962247)

  • Improved mood. Decreased anxiety.

  • Protects the brain, specifically with myelin formation (References:  PMID 17431228, 23647429, 29790373)

  • Improved HDL cholesterol and lower LDL cholesterol (References: PMID 9288699)

  • Decreases hot flashes (References: PMID 29962247)

*The PMID is the PubMed ID number that can be used to look up these references on



  • With synthetic progestin, breast cancer risk was increased by 9 more cases per 10,000 person-years of therapy in the WHI (Women’s Health Initiative study).  In other words, there was less than 1 additional case of breast cancer per 1000 users annually, a risk slightly greater than that observed with one daily glass of wine, less than with 2 daily glasses of wine, and similar to the risk increase from obesity, low physical activity, and other medications.  Synthetic progestin increases breast density which may make mammograms harder to interpret.  

  • A total of six studies were included in a large review of research studies. Five of the six studies reported no association between progestin-only formulations (including norethindrone oral contraceptives, depot medroxyprogesterone acetate, injectable, levonorgestrel system users, implantable and intrauterine devices) and breast cancer risk. Duration of use was examined in a few studies with heterogeneous results. Unlike studies of other oral contraceptives, studies indicate that progestin-only formulations do not increase the risk of breast cancer, although the literature is hampered by small sample sizes. Future research is needed to corroborate these findings, as further understanding of synthetic progesterone may initiate new prescription practices or guidelines for women's health. Breast Cancer Research And Treatment [Breast Cancer Res Treat] 2016 Jan; Vol. 155 (1), pp. 3-12. 

  • The E3N study of 80,000 post-menopausal women showed that synthetic progestin + estrogen slightly increased the risk of breast cancer but that natural progesterone + estrogen resulted in NO increased risk of breast cancer.  Reference:  Br Cancer Res Treat 2008; 107.

  • The emerging clinical epidemiological data support the hypothesis that progestogens are not a uniform class and that natural progesterone and synthetic progestins have different effects, with distinctive impacts on the risk of breast cancer diagnosis in menopausal women using HT.  Reference: Endocr Rev. 2013 Apr; 34(2): 171–208.



  • Observational evidence suggests that hormone therapy does not further alter the risk for breast cancer in women with a family history of breast cancer




Progestogen Glossary

  • Medroxyprogesterone (brand name Provera) - a synthetic progestin that is no longer used in many countries because of side effects. It is believed to have contributed to the increased risk of stroke seen in the WHI.  Provera is 300 times more potent than bio-identical natural progesterone.

  • Progestin - there are several hormones which fall into this broader category: progesterone, medroxyprogesterone, drosperinone

  • Progesterone - the bio-identical natural form of progestin which mimics exactly what women’s bodies produce before menopause

  • Prometrium - a brand of natural progesterone which is available at pharmacies.  It contains peanut oil. 










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