What is PCOS? Better understand this hormonal imbalance

1. Menstrual cycle and hormonal imbalance in women with PCOS

The menstrual cycle relies on precise hormonal regulation between the brain and the ovaries . This hormonal dialogue coordinates ovulation , fertility , and the proper sexual development of women.

Over an average period of 28 days, two major phases follow one another. The first, called the follicular phase (from day 1 to 14), begins with the secretion of GnRH by the brain, which stimulates the production of LH hormones in small quantities and FSH in larger quantities, the latter promoting the growth of follicles (sac-like structures located in the ovaries and in which the oocyte, the female reproductive cell, develops ).

Of these follicles, only one becomes dominant: it continues its maturation while the others degenerate.

In parallel, the increasing production of estrogen by the dominant follicle leads to a sudden surge in LH around day 14 of the cycle . This LH surge triggers ovulation, that is, the release of the oocyte from the mature follicle.

Next, the luteal phase (from day 15 to day 28) sees the ruptured follicle transform into the corpus luteum, which secretes progesterone and estrogen to prepare the uterus for a possible pregnancy . If fertilization does not occur, the drop in hormones triggers menstruation.

The entire process relies on a hormonal feedback mechanism that ensures its regularity . Polycystic ovary syndrome (PCOS) disrupts this regulation.

The imbalance between LH and FSH, marked by an excess of LH, prevents follicle maturation and blocks ovulation.

This imbalance also promotes an increased production of androgen hormones (male sex hormones such as testosterone) , which are normally present in small quantities in women.

2. What are the diagnostic criteria for PCOS?

The diagnosis of PCOS requires the presence of at least 2 of the following 3 Rotterdam criteria :

• clinical (acne, hirsutism, alopecia) and/or biological hyperandrogenism;
• ovulatory dysfunction (irregular menstrual cycles);
• polycystic ovaries on intravaginal ultrasound or high AMH levels.

a. Biological or clinical hyperandrogenism, what are the differences?

Clinical hyperandrogenism corresponds to the manifestations resulting from an excessive production of testosterone .

It manifests in approximately 70% of women with PCOS as excessive hair growth (hirsutism) , as well as acne and hair loss (alopecia) .

Hypertrichosis refers to excessive hair growth, most often fine, downy hair, generally in areas already hairy in women. In its most pronounced forms, it is called hirsutism, a dense and thick growth of hair that can appear on areas normally hairless in women, such as the face, chest, back, buttocks, or the front of the thighs.

From a biological point of view, hyperandrogenism is characterized by a free testosterone level ≥ 50 ng/dL .

b. Ovulatory dysfunction and irregular cycles

Hyperandrogenism , in addition to its cutaneous and hair-related effects, also influences the regularity of the menstrual cycle by disrupting ovulatory function , which frequently leads to cycle disorders.

This rarity or absence of ovulation (oligo-anovulation) causes irregular menstrual cycles , often longer than 35 to 40 days (oligomenorrhea).

Spaniomenorrhea, on the other hand, corresponds to a spacing of cycles greater than 6 to 8 weeks, which can evolve towards a total cessation of menstruation (amenorrhea).

These dysfunctions are the leading cause of infertility in women of reproductive age. Approximately 75% of women with polycystic ovary syndrome (PCOS) experience fertility problems.

c. Polycystic ovaries on intravaginal ultrasound or elevated AMH levels

Polycystic ovaries are characterized by the presence of numerous small, undeveloped follicles in the ovaries . Two methods can be used to identify them.

Transvaginal ultrasound : the fluid-rich follicles appear as black, round structures inside the ovaries, which are themselves visible as light gray on the image. The diagnosis is based on the presence of at least 20 follicles per ovary and/or an ovarian volume ≥ 10 mL .

Since 2023, blood testing for anti-Müllerian hormone (AMH) has been recognized as a diagnostic tool for PCOS. There is a strong correlation between the number of follicles observed on ultrasound and AMH levels. A value > 4.5 ng/mL strongly suggests PCOS. This test can complement or replace ultrasound.

3. What are the symptoms of PCOS?

There isn't just one type of PCOS, but several forms. Symptoms vary greatly from woman to woman . The condition can be mild or, conversely, very debilitating . It can significantly impact quality of life and daily functioning.

4. PCOS, what are the long-term risks and complications?

The symptoms of PCOS vary throughout life. In young women, the most frequent signs are related to hyperandrogenism and ovulation disorders . With age, these manifestations tend to lessen, while metabolic complications become more pronounced.

In the long term, PCOS can have significant health repercussions. It increases the risk of developing metabolic syndrome , which combines abdominal overweight, blood lipid abnormalities, high blood pressure, and glucose regulation disorders .

These factors promote insulin resistance , which can progress to type 2 diabetes , and constitute a risk factor for cardiovascular diseases, such as myocardial infarction or stroke.

Furthermore, excess androgens contribute to an accumulation of fat mass, which is itself implicated in the development of insulin resistance .

The risk of type 2 diabetes is thus three times higher in women with PCOS compared to those without. An increased risk of endometrial cancer before menopause has also been identified, although this risk remains low.

Finally, the psychological consequences should not be underestimated. PCOS is often associated with mental distress, particularly in the form of anxiety and depressive disorders.

5. PCOS: Understanding the root causes of this hormonal imbalance

The hormonal imbalances that cause PCOS are likely due to a combination of genetic and environmental factors.

a. PCOS and Genetic Influence

PCOS has a strong hereditary component. Between 60 and 70% of daughters whose mothers have the condition develop symptoms themselves.

To date, no single mutation has been identified as the "PCOS gene ". Approximately twenty predisposing genes are currently known, but they only explain a minority of cases, less than 10%.

In addition, certain environmental factors, including endocrine disruptors , are suspected of contributing to the development of PCOS, although no evidence has been established to date.

b. Impact of environment and lifestyle on PCOS

Oxidative stress , often linked to chronic inflammation , plays a key role in the development of PCOS. It results from an imbalance between the production of free radicals and antioxidant defense mechanisms, leading to damage to cells, lipids, proteins, and DNA.

Low-grade inflammation , or chronic low-intensity inflammation, is characterized by a moderate but persistent activation of the immune system. Unlike acute inflammation, this response develops over time, often without visible symptoms.

It is favored by:

• an unbalanced diet ,
• chronic stress,
• sedentary lifestyle,
• overweight,
• smoking,
• exposure to pollutants
• certain chronic diseases.

This background inflammatory state amplifies many disorders : fatigue, pain, weight gain, diabetes, cardiovascular diseases, neurodegenerative diseases, cancer, depression... Hence the importance of a varied and balanced diet, regular physical activity and a good lifestyle to limit these risk factors.