The baldness or androgenetic alopecia, is characterized by a lack, total or partial, of the hair.
Androgenetic alopecia or common baldness, is a thinning of the frontal-occipital part of the hairs, due to the miniaturization of the hair shaft.
It’s the most frequent type of alopecia: affects men and women of every race, with varying severity. There is a thinning, which can be more or less marked and more or less fast, that in men is located in the frontal-temporal area and / or to the tonsure, while in women is almost always distributed over the top of the head. The pathology is polygenic, with complete penetrance, and occurs much more in men than in women ( which, generally, also suffer at a later age, inasmuch the disease usually develops after menopause).
Androgenetic alopecia is linked to the activity of 5-alpha-reductase type II, which converts testosterone into dihydrotestosterone.
Endocrinopathies such as GH deficiency, hypothyroidism, menopause, polycystic ovary syndrome, virilizing tumors or treatment with androgens (although to tell the truth, it must be said that the only androgens that damage the scalp are dihydrotestosterone and androstenedione,- catabolite of testosterone- conversely testosterone has no harmful action against Hair) can cause baldness. Today, the cause of baldness is not mysterious anymore.
It has been ascertained that the origin of androgenetic alopecia lies in the effect of androgens hormones in hair bulbs. Are affected only the predisposed bulbs, typically localized in the frontal region and in the vertex. Therefore, the majority of people affected by androgenetic alopecia almost always maintains healthy hair in the crown area, which corresponds to the occipital and temporal areas of the head.
The miniaturization of the bulb takes place due to the transformation of testosterone in its most active metabolite, dihydrotestosterone (DHT). The miniaturization leads to the definitive death of the bulb and to permanent loss of hair. There is still no absolute certainty about the genes causing androgenetic alopecia, but the studies are getting closer to a resolution of the case.
It has been shown that most of the genes involved reside on the X chromosome, that is what the mother conveys to son, or what mother and father convey to daughter. Heredity to a son is greater
about the second X chromosome that the mother has inherited from his father, so the greater transmission takes place by his maternal grandfather to his grandson, rather than from father to son.