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DEFINITION
Baldness is an acute process of sudden hair loss which does not happen overnight. What really happens is the progressive miniaturization of hair, which means the transformation of thick hair (called terminal hairs) into increasingly shorter and thinner hair (called velus, or fuzz). In the evolution of the miniaturization process, we also observe the same amount of living roots, but these root generate smaller and weaker hairs. Therefore, the scalp can be seen through them. So, it´s usually at this stage that baldness becomes visually seen.
Baldness is also called ANDROGENETIC ALOPECIA. In men, it begins in the temporal region (the “high forehead”), and it evolves taking over all the top of the scalp up to the vertex (the “crown”). In women, the process is more diffuse, loss occurs in the central and upper regions of the scalp, without affecting the anterior line of hair implantation.
CLASSIFICATION
Male baldness is classified into seven main types, according to Hamilton-Norwood. For example, sub-type A is characterized when baldness evolves in the front region without forming a hair peninsula in the central region and simultaneously affecting the vertex (“crown”).
The genetic baldness
factor
Baldness is dominant autosome genetically transmitted, i.e., the presence of a gene, inherited from one of the parents, is enough for the child to present the pathology. If either the father or the mother suffers from baldness , the child has a 50% possibility of being bald as well. If both parents are bald (in the case of the mother it might be that her father is bald) chances increase to 75%.
By the analysis of the embryogenesis of hair, we notice that the area that will be affected by baldness (front region, top and vertex) has its origins in a certain region of the embryo called neural crest, and the area that will be immune to baldness (sides and the back of the head) are originated in another region of the embryo called mesoderm. The difference in embryonic origin between the area affected by AGA and the area immune to it influences the response of capillary follicles to DHT, i.e., only follicles in the front, intermediate and vortex regions possess receivers to link to the hormone, while follicles in the occipital region do not possess them, and therefore they never undergo miniaturization. This allows that baldness is treated for good through hair transplant.
Hormonal factor of
baldness
Sexual hormones play an important role in AGA. Testosterone reacts to an enzyme called type II 5-alfa-redutase type II found in the follicles, turn into dihydrotestosterone, or DHT. It´s known that men have 40% more receptors of 5-alfa-redutase in the front region and that they possess 3,5 times more 5-alfa-redutase than women. That explains why in most of the times male baldness begins in the front region.
DHT is five times more powerful than tetosterone. it´s the DHT that acts in the capillary follicles taking them to miniaturization of the hairs. Testosterone has its production increased during the beginning of puberty, for this reason, many AGA cases start during this period. The amount of testosterone is the same in bald and non-bald patients, even though the level of DHT is higher in the bald ones. There is no increase of Testosterone in the bloodstreams of bald patients, what happens is and activation the the sensibility of cellular receivers to DHT in patients that possess genetic inheritance to baldness.
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