In men, androgenetic alopecia results in the appearance of thinner and often less pigmented hair on the top of the head, which becomes lighter. This baldness may evenly affect the top of the skull, or begin by affecting the tip of the skull (the tonsure) or temples. Over time, the hair gradually gives way to a fuzz that disappears in turn.

Symptoms of androgenetic alopecia in women

Androgenetic alopecia can also be seen in women. In this case, the hair loss concerns the entire top of the head, in a diffuse way, sometimes sparing the frontal edge (the departure of the hair on the forehead). Contrary to what is observed in men, androgenetic alopecia in women is never complete: thinning hair persists.

Androgenetic alopecia can appear at any age in a woman's life, sometimes as early as puberty. It is often more pronounced in spring and fall. Most often, it occurs from menopause onwards.

How common is androgenetic alopecia?

In men, androgenetic alopecia becomes more common with age. It particularly affects men of European descent. In this population, it is estimated to affect 20% of 20-year-old men, 30% of 30-year-old men, 40% of 40-year-old men, and so on.

In women, androgenetic alopecia is rarer: one in five women around the age of 40, one in four women around the age of 60. Nevertheless, it accounts for 80% of long-term hair loss problems in women.

What causes androgenetic alopecia?

Androgenetic alopecia results from two factors: a genetic predisposition and the action of androgens, the male sex hormones (but nevertheless present in small quantities in women).

Genes predisposing to androgenetic alopecia have been identified, one of which is carried by the X chromosome (transmitted to males through their mothers). Thus, in men, the probability of suffering from baldness is higher when it is present in the maternal family.

In the presence of a favourable genetic background, the hair follicles on the top of the skull are particularly sensitive to the action of androgens, and in particular of a substance derived from testosterone (DHT, dihydrotestosterone). Under the action of this hormone, the hair growth cycle is accelerated and shortened. The hair becomes thinner, less dark and falls out faster. The 20 to 25 growth cycles that are supposed to last a lifetime are exhausted within a few years. The hair follicles on the sides of the skull are less sensitive to the action of the hormone and their growth cycle is less disrupted.

In women, other hormonal factors can promote androgenetic alopecia: oral contraceptives ("pill") or menopausal hormone treatments. In addition, stress and excess blood cholesterol could also be risk factors for alopecia in women.