The Protective Role of Progesterone

Updated: Apr 5

Darou Wellness - progesterone

Having optimal progesterone levels is very important for women’s health for many reasons, the most significant one being to balance out estrogen. Low progesterone can be associated with PMS, endometriosis, uterine fibroids, infertility, early miscarriage, PCOS, heavy periods and perimenopause. Having low progesterone is also associated with the development of breast cancer since this is the hormone that counterbalances estrogen.

What causes low progesterone?

Progesterone is a hormone that naturally declines with age, beginning somewhere in the 30’s and usually being more significant by age 38. This is why we see a much higher rate of estrogen-dominant conditions such as uterine fibroids, breast cysts, heavy menstrual flow and breast cancer with age.

Progesterone also can decline with prolonged periods of high stress. The reason is that both progesterone and the adrenal stress hormone cortisol share the same precursor hormone called pregnenolone. When you are going through a period of prolonged high stress, your body will use more pregnenolone to keep up with the demand for cortisol. This is also a way your body protects from getting pregnant during a period of high stress.

Progesterone may also appear low in cases of estrogen dominance. What this means is that there is a higher than normal level of estrogen, and not enough progesterone to counterbalance it. In these cases, the actual progesterone level may be normal but there are symptoms of low progesterone. The key here is to support estrogen breakdown and detoxification and reduce exposure to estrogen-mimicking substances like plastics (phthalates, BPA), pesticides, hormones in meat or dairy and other chemicals found in personal care products (such as paragons and DEA).

Signs of low progesterone include:

  1. Spotting before your period

  2. Menstrual cycles shorter than 27 days

  3. Very heavy menstrual flow

  4. Premenstrual syndrome, especially with poor sleep and anxiety

  5. Difficulty conceiving

  6. Early miscarriage (before 7 weeks)

  7. Lots of perimenopause symptoms – mood swings, difficulty sleeping, heavy and difficult periods, irregular cycles.

How is progesterone tested?

Progesterone can be tested very simply with a blood test. The reference range is huge, but here is what the numbers mean when tested mid-luteal phase, meaning approximately one week before your next period is due:

  1. > 50 nmol/L – high or pregnant

  2. 40 – 50 nmol/L – optimal

  3. 33-40 nmol/L – suboptimal

  4. < 33 mmol/L – low

How is low progesterone treated:

As a naturopathic doctor, my aim is to treat the root cause whenever possible. This means that our first recommendations will be nutrition, stress reduction and possibly herbal medicines. In some cases where the hormone imbalance or symptoms are extreme, we do have the option of bioidentical progesterone.

Nutrition: Increasing fibre in the diet, adding more vegetables, especially the broccoli family of vegetables, and reducing caffeine, alcohol and sugar are some of the basics. Switching to a more organic diet will also reduce exposure to estrogen-mimicking chemicals which can promote estrogen dominance.

Adrenal gland support: Since low progesterone may be due to the body needing extra cortisol to deal with stress, it is essential to look at stress reduction as a significant treatment for low progesterone. Dropping progesterone levels is one way your body reduces your fertility at times of chronic high stress.

Reducing exposure to estrogen-mimicking chemicals: We are exposed to many chemicals through our foods, personal care products and plastics which mimic estrogen and increase our estrogenic load. Switching to organic, choosing natural personal care products and minimizing the use of plastics is an excellent start.

Supporting estrogen metabolism and detoxification: Estrogen is detoxed in two phases, first through the liver and second through the colon. What this means is that we need to support liver detoxification and also bowel health, to optimize hormone balance.

Herbs to increase progesterone: The next step may be herbs to increase progesterone, such as Vitex, wild yam, Rehmannia and white peony.

Bioidentical progesterone: Progesterone can be prescribed as a cream, orally, and in cases of fertility as vaginal suppositories. The benefit of bioidentical progesterone is that it is structurally identical to the progesterone your own body produces, and we can dose it precisely to optimal physiological levels. In cases of difficulty hormone imbalance such as endometriosis and perimenopause, this is often the most effective treatment.

The safety of bioidentical progesterone:

There have been several studies with the use of bioidentical hormones, and the use of progesterone as opposed to synthetic progestins has been shown to be not only safe, but also protective(1). In fact, the use of human identical progesterone slows the growth of estrogen-receptor and progesterone-receptor positive breast cancers (2) Furthermore, low progesterone levels alone appear to be associated with the development of breast cancer. John Hopkin’s University Medical School followed 1000 women who were treated for infertility over 20 years. They divided women into two groups: 1) Infertility associated with deficiency of progesterone; and 2) Women with normal progesterone levels. The results were that in the progesterone deficient group, there was a 5.4 fold increased risk of premenopausal breast cancer, and a 10 fold higher rate of death from cancer of all kinds (3). Optimizing progesterone levels appears to be an important step in cancer prevention. In regards to cardiovascular risk, again we find that progesterone has a protective role. In a review article (4), the use of bioidentical progesterone progesterone post-menopause was found to:

  1. Lower Blood Pressure

  2. Help control Insulin and Glucose levels

  3. Improve Cholesterol profiles

  4. Reduce Heart Disease risk factors associated with inflammation

  5. Help prevent Blood Vessel Spasms

  6. Does not increase risk of Stroke

  7. Protect the Brain and the Nervous System

In conclusion

As you can tell, progesterone is a very important hormone and it is a key treatment point in many women’s hormone related health conditions. If you suspect that low progesterone or estrogen dominance with relative low-progesterone may be affecting your health, the first step is testing your hormones, ideally with a saliva panel to look at the balance between estrogen and progesterone. From there we have many options, ranging from nutrition changes, to improving digestive health, and then with herbal medicine or bioidential hormones. This is however an are of hormone balance where we can see profound improvements in your overall health and well-being.


1. Fournier A, Berrino F, Clavel-Chapelon. Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study. Breast Cancer Res Treat. 2008;107(1): 103-111. 2. Mohammed H, Russell A, Stark R et al. Progesterone receptor modulates Era action in breast cancer. Nature 2015. doi:10.1038/nature 14583. 3. Cowan LD, Gordis JA, Tonascia JA, Jones GS. Breast cancer incidence in women with a history of progesterone deficiency. J Epidemiol. 1981;114:209-217. 4. Hermit M, Simoncinib T, Fullera S, Genazzanib AR. Could transdermal estradiol + progesterone be a safer postmenopausal HRT? A review. Maturitas. 2008; 60(3):185-201

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