Why Progesterone Is Just as Important as Estrogen

It’s time to bring progesterone into the conversation about women’s health. That’s according to Canadian endocrinology professor Jerilynn Prior in her paper “Women’s reproductive system as balanced estradiol and progesterone actions—a revolutionary, paradigm-shifting concept in women’s health.” In the paper, Professor Prior makes the case that historically there has been a “cultural over-emphasis on estrogen” while “progesterone tends to be ignored or associated with negative effects.”

How science got it wrong about progesterone

Progesterone has been both ignored and mistakenly blamed for side effects it does not cause. How did that happen?

For starters, progesterone was discovered after estrogen and so missed the opportunity to be part of the perfect hormone dichotomy of “testosterone for men and estrogen for women.”

Next, early preparations of progesterone were poorly absorbed orally so progesterone was of little interest to “the estrogen-discovering scientists, the estrogen-treating clinicians and the estrogen-making pharmaceutical manufacturers, [who] all worked together.” (Modern preparations of oral micronized progesterone can be absorbed orally.)

Finally, progesterone was rapidly replaced by synthetic progestins in both research and treatment even though progestins have different (and sometimes opposite) effects compared to progesterone. The side effects and risks of progestins have since been mistakenly attributed to progesterone. (For example, progestins increase the risk of breast cancer, but progesterone reduces the risk.)

Estrogen and progesterone work together to build long-term health

Women have two main ovarian hormones, not one; and physiologically, estrogen and progesterone work as a team. For example, the pre-ovulatory surge of estrogen (estradiol) is necessary for ovulation and the manufacture of progesterone. Estrogen also works in every tissue to promote progesterone receptors.

In turn, progesterone counterbalances estrogen in all parts of the body including:

  • the uterus, where progesterone thins the lining, while estrogen thickens it;
  • the brain, where progesterone is calming, while estrogen is stimulating;
  • the breasts, where progesterone helps to slow cell division, while estrogen increases cell division.

Progesterone can also promote ovulation by providing important hormonal feedback to the hypothalamus.

👉🏽 Did you know? On a blood test, a good peak luteal phase progesterone level is 80 nmol/L which is 100 times more than an average peak estradiol level of 800 pmol/L (0.8 nmol/L).

Together, estrogen and progesterone promote the long-term health of the brain, bones and cardiovascular system. As Professor Prior says in her paper, “normally ovulatory cycles across a woman’s long reproductive life span are needed to prevent osteoporosis and fracture, heart attacks, and breast and endometrial cancers during women’s older years.” In fact, each and every ovulatory cycle is like a deposit into the bank account of long-term health.

Estrogen and progesterone for long-term health.

Do you make enough progesterone?

A regular ovulatory menstrual cycle is the only way to make progesterone.

Definition: An ovulatory cycle is a menstrual cycle in which your basal body temperatures go up with ovulation and stay up for at least 11 days, indicating a healthy luteal phase.

Progesterone deficiency is caused by:

Progesterone as treatment

As Professor Prior explains in her paper, the first step to reclaim progesterone is “to make visible progesterone’s… presence or absence” in a menstrual cycle. This can be done by tracking ovulation with temperatures and/or an at-home progesterone test. Knowing if and when you ovulate is called body literacy.

If progesterone is absent, ovulation (and progesterone) can be restored by reducing stress, eating enough, and promoting optimal general health. See Roadmap to progesterone.

👉🏽 Tip: According to the American College of Obstetricians and Gynecologists (ACOG), ovulation is an expression of general health or a “monthly report card.”

If ovulation cannot be easily restored, there is also the option to take progesterone as cyclic progesterone therapy, which is a promising treatment for PCOS, irregular cycles, and the heavy bleeding of perimenopause.

For more information about progesterone and PCOS, see my paper The central role of ovulatory disturbances in the etiology of androgenic polycystic ovary syndrome (PCOS)—Evidence for treatment with cyclic progesterone.

For more information about progesterone and perimenopause, see my book Hormone Repair Manual.

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