Micronized Bioidentical Progesterone for PCOS and Regulating Periods

What is progesterone?

Progesterone is a hormone that is primarily produced by the corpus luteum, only after ovulation has occurred. Once the follicle releases the egg, the follicle will become a corpus luteum that will produce progesterone to help maintain a pregnancy if the egg gets fertilized. If the egg that is released does not get fertilized, progesterone will fall and that is when your menstrual cycle will start. Additionally, a small amount of progesterone is also produced in your adrenal glands.

When we look at a woman with PCOS, overall the exposure to progesterone is low over the year if you experience irregular cycles. If the first part of the cycle is really long, and ovulation is later, the amount of progesterone overall that will be produce in a year will be less than someone who ovulates every 14 days.

How does Micronized Bioidentical Progesterone differ from a Progestin? 

A Progestin is known as a synthetic form of progesterone that is not bioidentical which is commonly found in birth control pills and depo-provera (aka medroxyprogesterone acetate). Bioidentical, meaning it is just as similar to the progesterone we naturally produce in our bodies. Micronized refers to the delivery of progesterone, it is in a very small form so that it can pass through the digestive system and get into the bloodstream when taken orally.

Benefits of Micronized Bioidentical Progesterone

  • Protects against endometrial hyperplasia (aka thickening of lining)
  • Supports implantation and early pregnancy
  • Improves sleep and calms the nervous system
  • Increases T4 hormone in the thyroid
  • Supports bone formation
  • Protects the blood vessels for cardiovascular health
  • In PCOS, helps to reduce testosterone to allow for ovulation to occur at the appropriate time

How does cyclical progesterone actually work to stimulate ovulation, not just a withdrawal bleed?

It all comes down to proper maturation between the brain and ovary. This does not occur well in some women that have PCOS during puberty, so then we see chronic dysfunction of the HPO (hypothalamic-pituitary ovarian) axis.

The hypothalamus releases a hormone call GnRH and this stimulates the production of FSH and LH from the anterior pituitary in the brain. It all comes down to the so-called pulsing of GnRH in the hypothalamus. The slow pulsing of GnRH from the brain allows for FSH to become more prominent. And remember FSH allows for the production of estrogen which allows for the follicle to grow and helps us to ovulate. Fast pulsing of GnRH causes LH to be produced. LH stimulates the ovary to produce testosterone.

In early puberty, we are more dominant in LH, testosterone. The natural process will be kickstarted where FSH will be produced, ovulation will happen, we will be exposed to progesterone and this will help to bring down the pulsing of GnRH to allow us to create FSH on the next cycle = good thing!

In PCOS, we have more insulin, which leads to more androgens, we see high LH:FSH ratios, less progesterone and we don’t get a natural induction of cycles. GnRH is constantly pulsing, releasing LH.

The goal is to bring androgens and LH down.

Exposing the body to progesterone will help to essentially decrease testosterone, reduce GnRH pulsing and allow for FSH to rise in the next cycles to come to allow for ovulation.

Cyclical Progesterone Therapy – What is this?

Cycling the progesterone on and off allows for normal cycles in states of chronic low progesterone-like PCOS, which will help to mimic the natural pattern of progesterone. For example, bioidentical progesterone will be started on cycle day 14-18 (cycle day one is the first day of your period) for 14 nights then we will wait for a period to come.

Typically, it can take 9-12 cycles to get enough exposure to progesterone to regulate the cycle.

Types of Micronized Bioidentical Progesterone

a. Transdermal aka topical progesterone: low levels in the bloodstream as it is harder to absorb from the skin, less useful in cyclic progesterone therapy because the dose is so low to have an effect

b. Oral Micronized Progesterone: higher rise in the bloodstream levels, can cause fatigue and grogginess which can be helpful for insomnia

c. Vaginal suppositories: mostly delivered into the uterine environment beneficial for Endometriosis, dysmenorrhea, menorrhagia, protecting the uterine environment. Levels are stable in the bloodstream.

What dose is common to help regulate cycles in women with PCOS?

100-300 mg typically from the research by Dr. Jerilynn Prior and her research centre CEMCOR using oral micronized progesterone

In my experience using 300mg progesterone vaginal suppositories also works well.

Who can prescribe micronized progesterone?

Naturopathic doctors who have prescribing rights, OBGYN, Medical Doctors, Reproductive Endocrinologists, Endocrinologist

Want to learn more or see if micronized bioidentical progesterone is right for you? You can consult with Dr. Samina Mitha, ND by using her Contact page. 


McCulloch, D. (2020). Prescribing for PCOS. Presentation, Online.

The Centre for Menstrual Cycle and Ovulation Research. (2021). Retrieved 26 October 2021, from https://www.cemcor.ubc.ca/

Scroll to Top