A man looking at thinning hair at the temple

Androgenetic alopecia is the most common form of hair loss. It is a hereditary, gradual thinning linked to the sensitivity of hair follicles to male sex hormones. It occurs in both men and women, it simply looks different.

How it develops

In the skin of the scalp, the enzyme 5-alpha-reductase converts testosterone into dihydrotestosterone, DHT for short. In people who have inherited the sensitivity, follicles in certain zones of the head respond to DHT by gradually shrinking.

That process is called miniaturisation. The follicle does not disappear all at once: with each cycle it becomes smaller, the growth phase shortens, and the hair that grows is thinner, shorter and lighter. After enough cycles the hair becomes so fine that it is practically invisible.

This is why androgenetic alopecia develops over years, and why in the early stage it is noticed as my hair seems somehow thinner rather than as loss.

Why particular zones

Sensitivity to DHT is not the same across the whole head. Follicles at the back and sides are usually resistant, while those on the crown and along the front hairline are sensitive.

That explains why the pattern of thinning repeats itself across different people, and why hair transplants use precisely the hairs from the back of the head.

How it looks in men

In men the process usually begins with the front hairline receding above the temples, followed by thinning at the crown. Over time those two zones merge.

The Norwood scale is used to describe the degree. It has several stages, from mild recession of the hairline to complete loss of hair on the top of the head, with a rim retained at the sides and back.

How it looks in women

In women the pattern is different. The front hairline usually stays intact, and the thinning appears diffusely along the middle of the head. The first sign is normally a widening parting: a parting that used to be narrow gradually becomes wider, in a shape often described as a Christmas tree.

The Ludwig scale, with three grades of density, is used to describe it.

In women it is important not to skip checking for other causes. Iron deficiency, thyroid disorders and telogen effluvium give a similar impression of diffuse thinning, yet they are treated in completely different ways. We wrote about this in Hair loss.

What speeds it up and what has no effect

Genetics determines whether the condition will develop and to what extent. That does not change.

The course can be influenced by general health, diet, smoking and other causes of shedding that overlap with androgenetic alopecia, for example an iron deficiency that appears at the same time.

What has no effect: hats, frequent washing, haircuts, the choice of shampoo.

How it is monitored

Androgenetic alopecia develops slowly, so subjective impressions are unreliable. What helps:

  • a photograph of the crown and the parting once a month, always in the same light and from the same angle
  • a trichoscopic examination by a dermatologist, which shows the difference in hair thickness, the main sign of miniaturisation
  • patience in assessing it; changes are judged over months, not weeks

What is done about it

There are preparations classed as medicines that are used for this condition. A doctor decides on them, because they come with instructions, side effects and situations in which they are not recommended. We described one of the best known in Minoxidil.

There are also procedures carried out in a clinic, as well as surgical transplantation. Those are medical decisions.

Scalp care and cosmetic products are a third, separate category. They deal with the condition of the skin and the appearance of the hair and are not a substitute for either of the above. We described what they contain in Hair serums and ampoules.

When to see a dermatologist

If you are not certain that this is hereditary thinning, an examination makes sense, particularly if the shedding started suddenly, if it comes with changes on the scalp, or if it appears in limited patches. Those are signs of other conditions described in Alopecia.

In short

Androgenetic alopecia is a hereditary, gradual shrinking of the follicles under the influence of DHT. In men it shows as a receding hairline and a thinning crown, in women as a widening parting. It develops over years, it is monitored with photographs and examination, and decisions about treatment are made by a doctor.