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Androgenetic Alopecia

The androgenetic alopecia (also known as baldness) is a condition of total or partial lack of hair. There are different scales in order to measure the extension of baldness: here we will mention two of them:

  • Hamilton’s scale
  • Norwood’s scale

People who belong to the first level of the Hamilton scale do not suffer from baldness.
The androgenetic alopecia or common baldness, is the reduction of the occipital front of the hair, due to the miniaturiziation of the stem. It is the most common type of alopecia: it affects men and women of every race,with different seriousness. It is more frequent in the caucasian race and usually it affects men, not women. In other races it is less present.It doesn’t affect Eunuchs.
The androgenetic alopecia is linked to the activity of the 5alpha-reductase type II, which transforms testosterone in dihydrotestosterone. Endocrinopathies as the lack of GH, hypothyroidism, menopause, polycystic ovary syndrome, virilizing tumors or treatment with androgens (although saying the truth, we have to say that the only androgens, which damage the scalp, are the dihydrotestosterone and the androstenedione- catabolites of the testosterone- , on the contrary testosterone do not have any damaging action against hair) can produce baldness. Also the belief that baldness is hereditary is totally untrue; however, also in this case the hereditary factor is not completely imputable to genetics, but to surroundings; to confirm this , younger brothers have demonstrably more probabilities to run into baldness than older brothers; this happen because of the sorrounding differences in the education and in the familiar hierarchy, despite having the same genetic predisposition to suprarenalism. This demonstrate the main cause of baldness that stays in an increased hypophysialis activity, which is expressed in an ipersuprarenalism; it means chronic high levels of catabolic hormones (adrenaline and cortisol) , as well as of ACTH, typical of stress conditions; not by chance baldness is typical of suprarenalic or hypophysialic pathologies like pheochromocytoma and the Chushing disease, that are the only cases that affect indiscriminately men and women. Under this point of view, the primary cause of baldness would stay in the peripheral vasoconstrictor action of those hormones and the scalp is peripheral; so baldness is due to atrophy of capillary vessels, which feed the follicle. To confirm this, we have the aetiology, the typical evolution of bald. Unlike what we believe , future bald is predictable and already established at the age of 13-14 (the only exceptions, in ripe age, are secreting deseases, that have been said before) preceeded at that age by dandruff, clear symptom of epidermic suffering, caused by the capillary vessels’ atrophy and so then chronic malnutrition of the follicle and of the epithelium. Putting the attention of baldness’ causes on testosterone’s catabolites is totally misleading because their mayor levels are a symptom and not the cause of the predispositon to baldness; indeed the high catabolites’ levels of the testosterone are due to the antagonistic activity of adrenocortical hormones , that eliminate testosterone (that as androgen hormon is instead beneficial for the hair) transforming it in an inactive dihydrotestosterone. So the difference between males and females would stay in a very accurate logic, that is that males, secreting mayor quantities of testosterone, consequently secrate also mayor quantities of its antagonists ( the hematic presence of testosterone stimulate the secration of its antagonists; paradoxically for this reason also virilizing tumors cause baldness). A further confirmation of this, is the fact that baldness is usually found together with other typical effects of the hormones of the adrenal cortex , in which we can find the above-mentioned adolescent danduff, and in particular teenage acne.
The fundamental pathological process consists in the acceleration, under androgenetic impulse, of the mitotic phase of the pilaris cycle (anagen I-V) and the following reduction of the differentiative phase, that normally is very long. Being this one, necessarily incomplete, the stem wiil be slimmer and short (vellus). Also in older age, atrophical phenomena of the scalp overlap, making it slimmer and shiny. In this phase all the ”vellus” desappear. A second pathological process consists in the loss of individuality of the cycles papillary (property of a normal adult scalp) and so then of their synchronization. This phenomenon is caused by the reduction of the duration of the phase of differentiation. A third phenomenon is the growth of the Kenogen’s phase: when the hair shaft falls off the end of the telogen,the follicle has already been occupied by another in an advanced anagen. It may be appear a break between the fall of the hair in telogen and its replacement with the new in anagen: during this physiological break (kenogen), the follicle stays empty.
In the androgenetic baldness are lost only the hair that are situated in the frontal region, because in this area the alpha 5-reductase is more active, so there is an higher quantity of DHT. Besides this, it is also the most peripherial part of the scalp’s blood circulation, and so the one that more face the atrophy of the vessels. The cause of the androgenic alopecia is the dihydrotestosterone (DHT) (full name: 5 alpha-dihydrotestosterone, shortened 5a-DHT:INN: androstanolone).It is a metabolite biologically active of the testosterone hormon. Besides favouring the growth of the body hair and the beard, it can also negatively affect prostate and also hair. DHT is already produced by males in the womb and it is the responsible of the formation of characters of the male gender. DHT actively contributes also at the formation of other caractheristics generally of males, included hair growth and the depth of the voice.
Regardless, a critic factor is feeding the bulbs. The most pheripheral area of blood circulation is the scalp and so it is the most affected area damaged by the effects of pheripheral vasoconstrictor hormones.
In the clinical course we see a reduction, that can be more or less marked and more or less fast,in men it is located in the frontotemporal area and /or tonsure, while in women is almost always distributed over the whole superior part of the head. We can often assist in man in a parallel increase of the hair body. Generally the patient mourns a rise on the hair’s fall. The pathology is polygenic, with complete penetrance and it occurs much more in men than women (women that, generally, suffer it also in ripe age, because the pathology tends to develop after the menopause).