Alopecia

«Hair and hair growth

Alopecia: from the Greek "alopex" = fox, term used to emphasize the similarity with this animal, which loses its hair twice in a year.

There are two main types of alopecia, telogenic and androgenic.

The first involves, usually in a short time, a limited or generalized hair loss, in response to strong physical or psychological stress. This type of alopecia, which can affect both men and women, is reversible. Between the two, it therefore represents the "beneficial" form.

The other type of alopecia is called androgenic, to emphasize that it mainly, but not exclusively, affects men. In these cases, the term "losing hair" is not entirely correct, since the hair follicles, while undergoing a gradual process of involution, which leads the hair to lose its terminal appearance and to acquire the characteristic features of the fleece (very thin, soft and depigmented hairs), remain numerically the same. Contrary to what has been said for the telogenic form, androgenic alopecia is irreversible.

With advancing age, physiologically, the hair follicles present on the forehead and temples undergo a gradual process of involution, with consequent thinning of the hair present in these areas. This phenomenon is valid for both men and women, where the problem, although less evident, is accentuated after menopause.

Androgenic alopecia can also clearly affect women of childbearing age, almost always due to important hormonal alterations. In many cases there is in fact a higher than normal level of typically male hormones, first of all dihydrotestosterone.

The etiology of androgenic alopecia has not been clarified, although some things now seem certain.For example, it has been shown that, for it to occur, the presence of androgens is necessary; for this reason a child will never suffer from androgenic alopecia. It has also been observed that in men predisposed to baldness the activity of 5-α- reductase is greater than normal. The same enzyme, which promotes the transformation of androstenedione into dihydrotestosterone, stimulates the secretion of the sebaceous glands. An excess of sebum (see greasy hair) tends to weigh down and remove vitality from the hair, but does not directly atrophy the follicles. the term seborrheic alopecia has now fallen into disuse.

Numerous hypotheses have been advanced on the "etiology of" alopecia, let's see two.

Some hypothesize that in the follicles of subjects predisposed to baldness, there is an accumulation of a substance with an inhibitory action, which accelerates the frequency of growth cycles. This substance would be produced during the anagen phase and would imply a rapid transition from the growth phase to the telogen phase. Due to this phenomenon, the size of the follicle would reduce cycle after cycle, making the hair increasingly fragile and thin.

A second hypothesis assumes that at the base of alopecia there is an inflammatory process at the level of the bulbs. In response to this phenomenon, autoantibodies would form, which would block the activity of the matrix, that is, of that group of cells which, by dividing, allows hair growth. The production of these autoantibodies would be genetically dictated.

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