A hair appears, grows, then dies. And then the hair falls out.
This hair cycle lasts on average 3 years for men and 5 years for women. What is less commonly known is that this cycle is only repeated 25 times. If these cycles keep a regular rhythm, we are supposed to have a "normal" amount of hair throughout our lives.
But, in the case of progressive hair loss, this rhythm is accelerated. Cycles become shorter and shorter, at the risk of coming to an early end.
In fact, once it has reached exhaustion, at the end of the 25 cycles, the hair follicle dies. It resorbs and then disappears.
At this stage, only surgery can provide a solution, a hair transplant, for example. It is therefore important to take alopecia seriously as soon as possible: when there is still time to re-grow hair.
Why does the rhythm of the hair cycles go so fast?
Progressive hair loss is the result of a dysfunction, often genetic, of the hair and scalp in response to certain male hormones: androgens. This dependency on hormones also explains why this phenomenon only begins after puberty.
Testosterone is involved, but indirectly.
To cause hair loss, testosterone must first be converted by 5α-reductase to dihydrotestosterone (DHT).
Hyperactivity of this enzyme leads to an overproduction of DHT, which will cause a shortening of the hair's life cycle and, therefore, an acceleration of the hair's cycles.