Hormonal balance plays a fundamental role in hair health. Even a slight imbalance can disrupt the hair cycle and cause diffuse, persistent, or cyclical hair loss.
In fact one of the most frequent, yet most underestimated, causes of female alopecia.
At each major stage of life, hormones change... and hair follows suit.
Key periods at risk
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Puberty
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Hormonal contraception (starting or stopping)
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PCOS (polycystic ovary syndrome)
How hormones affect hair
Our hair follicles are extremely sensitive to hormonal fluctuations . Each hormone influences, directly or indirectly, hair growth, thickness, and density.
The main hormones involved:
- Estrogens
As dominant female hormones, they prolong the hair growth phase (anagen phase) and protect the follicles against the action of androgens. - Progesterone
Present after ovulation and during pregnancy, it can antagonize low doses of androgens. - Testosterone
Also present in small quantities in women. It can be converted into DHT, the key molecule in hormonal decline. - DHT (dihydrotestosterone)
An active derivative of testosterone, it is the main factor in androgenic alopecia . It progressively miniaturizes the follicles, preventing regrowth. - Cortisol (stress hormone)
In excess, it disrupts the hair cycle and can cause telogen effluvium (diffuse hair loss), while also affecting scalp microcirculation. - Thyroid hormones (T3, T4)
A thyroid imbalance slows hair growth, weakens the fiber, and promotes diffuse hair loss. - Insulin
Insulin resistance (common in PCOS) stimulates androgen production, promoting androgenic-type hair loss. - Prolactin
In excess, it can disrupt the overall hormonal balance and promote hair loss.
Hormonal contraception and hair loss
The pill artificially alters hormone levels, which can influence the hair cycle.
Two types of pills
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Combined pills (estrogen-progestin): often stabilizing during use, but a drop may occur when stopping.
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Progestin-only pills : some have an androgenic effect and can promote DHT production.
What is actually happening
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During the course of treatment : hair loss may be stabilized or worsened depending on the pill.
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When stopping : sudden drop in estrogens → rebound effect of androgens → pronounced drop.
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In the long term : in predisposed women, some pills can accelerate latent androgenic alopecia .
Postpartum: an impressive but temporary fall
After childbirth, the drop in estrogen causes hair loss called postpartum telogen effluvium.
It usually occurs 2 to 4 months after birth , diffusely across the entire scalp.
Although it is impressive, this hair loss is physiological and reversible : the follicles remain active and regrowth is possible, provided the scalp is properly supported.
PCOS: When excess androgens weaken hair
PCOS (polycystic ovary syndrome) is primarily a hormonal imbalance characterized by an excess of androgens, so-called "male" hormones naturally present in women in small quantities.
It affects approximately 7 to 10% of women and is often accompanied by androgenic type hair loss.
This excess of testosterone and DHT leads to increased binding of these hormones to the hair follicles, which gradually shrink, particularly at the top of the head.
The part widens, the hair thins and the density slowly decreases, sometimes over several years, making the loss difficult to spot at the beginning.
This hair loss is frequently accompanied by other signs of PCOS: irregular menstrual cycles, acne, weight gain, or excessive hair growth (hirsutism).
Menopause: when estrogen protection disappears
During menopause, hair loss becomes more frequent due to the drop in female hormones.
The follicles then become more sensitive to DHT , which leads to progressive thinning , particularly in the forehead and the top of the head.
Hair becomes thinner, more fragile, with an overall loss of density.
Stress and hair loss
Stress, whether sudden or chronic, directly affects the hair cycle.
Increased cortisol disrupts hormonal balance and can indirectly stimulate DHT production.
Result: the hairs prematurely enter the shedding phase, causing diffuse telogen effluvium .
It's a survival mechanism: the body prioritizes vital functions at the expense of hair growth.
Hormones influence every stage of the hair's life cycle. Understanding their role is essential to identifying the true cause of hair loss and implementing a targeted routine, adapted to the scalp, and not just the lengths.