Permanent hair loss
Baldness, from the latin calvus (bald) is defined as the permanent absence of hair on the head. We talk about partial baldness when permanent hair loss concerns an area of hair such as gulfs. On the contrary, baldness is total when only the hair of the crown is left out, that is the hair at the bottom of the head: it is baldness said to be hippocratic (this name is drawn from the reknown Antiquity doctor Hippocrates who had this type of alopecia).
It should be noted that the hair of the crown never falls, compared to the rest of the hair.
This phenomenon occurs as the hair of the crown has a genetic specificity that is different from the other hair. This is going to allow protecting hair from the harmful effects of androgen.
Androgenic alopecia (i.e baldness) calls to mind the origin of this hair disorder: androgen and genetics. Androgen are the male hormones and genetics represent personal and family history.
Androgen are made at the start of puberty. With regard to hair, it is the male hormone dihydrotestosterone (DHT) which acts onto the hair cycle. This hormone is going to act unreasonably on hair cells. Indeed, DHT is going to hyper-sensitise hair follicles, which is going to result in an acceleration of hair cycles so that its stocks are going to more or less run out fast, generating the permanent disappearance of hair.
"Hairless : Why do we lose hair ?" (video 1:02s)
Today baldness affects about 70% of men and can appear as soon as 18/20 years old.
It generally results in scarcity of hair at the level of the temporal gulfs
which are going to accentuate little by little by a decline of the central hair line.