What is PCOS? Better understand this hormonal imbalance

Menstrual cycle and hormonal imbalance in PCOS women

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 occur. 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 the hormones LH 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 oocytes , female reproductive cells, develop .

Among these follicles, only one becomes dominant: it continues to mature while the others degenerate.

At the same time, the increasing production of estrogen by the dominant follicle leads to a sudden surge of LH around day 14 of the cycle . This surge of LH triggers ovulation, i.e. the release of the oocyte from the mature follicle.

Then, the luteal phase (from day 15 to 28) sees the ruptured follicle transform into a corpus luteum, which secretes progesterone and estrogen to prepare the uterus for a possible pregnancy . In the absence of fertilization, the drop in hormones leads to 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 the maturation of follicles and blocks ovulation.

This disruption also promotes increased production of androgen hormones , male sex hormones such as testosterone , normally present in low amounts in women.

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

Biological or clinical hyperandrogenism, what are the differences?

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

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

Hyperpilosity refers to excessive hair growth, most often downy hair, usually in areas that are already hairy in women. In the most severe forms, we find hirsutism, a dense and thick hair growth that can appear on areas normally devoid of hair in women, such as the face, chest, back, buttocks or the front of the thighs.

Biologically, hyperandrogenism is characterized by a free testosterone level ≥ 50 ng/dL .

Ovulatory dysfunction and irregular cycles

Hyperandrogenism , in addition to its cutaneous and hair 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 extended beyond 35 to 40 days (oligomenorrhea).

Spaniomenorrhea corresponds to a spacing of cycles greater than 6 to 8 weeks, which can develop into a total interruption of periods (amenorrhea).

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

Polycystic ovaries on intravaginal ultrasound or high AMH level

Polycystic ovaries are characterized by the presence of numerous small, undeveloped follicles in the ovaries . There are two methods for identifying them.

Transvaginal ultrasound : Follicles, rich in fluid, appear as black, round structures inside the ovaries, themselves visible in light gray on the image. 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 the AMH level. A value > 4.5 ng/mL strongly suggests PCOS. This test can complement or replace ultrasound.

What are the symptoms of PCOS?

There is not just one PCOS, but several forms of PCOS. These symptoms vary greatly from one woman to another . The disease can be subtle or, on the contrary, very disabling . They can significantly affect quality of life and daily life.

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

PCOS symptoms vary throughout life. In younger women, the most common signs are related to hyperandrogenism and ovulation disorders . With age, these symptoms tend to diminish, 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 excess weight, blood lipid abnormalities, high blood pressure and impaired glucose regulation .

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

In addition, excess androgens contribute to an accumulation of fat mass, which is itself involved in the development of insulin resistance .

The risk of type 2 diabetes is thus multiplied by three 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 suffering, particularly in the form of anxiety and depressive disorders.

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.

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 a "PCOS gene ." Around twenty predisposition genes are now known, but they only explain a minority of cases, less than 10%.

In addition, certain environmental factors, notably endocrine disruptors , are suspected of contributing to the development of PCOS, without established proof to date.

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 free radical production and antioxidant defense mechanisms, leading to damage to cells, lipids, proteins and DNA.

Low-grade inflammation , or chronic low-intensity inflammation, is characterized by moderate but persistent activation of the immune system. Unlike acute inflammation, this response lasts 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 underlying inflammatory state amplifies many disorders : fatigue, pain, weight gain, diabetes, cardiovascular and neurodegenerative diseases, cancer, depression, etc. Hence the importance of a varied and balanced diet, regular physical activity, and a healthy lifestyle to limit these risk factors.