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THE HAIR LOSS PROCESS
The mechanism by which men lose their hair is better understood than the same process for women. The extent to which someone is affected by male pattern baldness is determined by a combination of genetic factors and androgens, specifically, the circulating male hormones testosterone and dihydrotestosterone (DHT). Unlike earlier reports, we now know that the tendency for male pattern baldness can be inherited genetically from either side of the family.
In men, hair loss can start any time after puberty, usually in the late teens to early 20's. Typical male pattern hair loss starts as a recession of the hairline with some thinning in the crown. This can eventually progress over years or decades, to the familiar 'monk's ring' of hair.
In general, women tend to see a slightly different pattern and different time of onset of hair loss. Female pattern hair loss starts in the late 40's to 50's, usually without a recession of the hairline. Some women experience just a thinning of density up top, and others tend to thin out over broader regions or the entire scalp. Scientists are unsure of the exact causes of female pattern hair loss, but feel it is related to hormonal changes.
As previously mentioned, the hair loss process in men is better understood. As a man ages, "genetically sensitive" follicles on the scalp begin to miniaturize in the presence of normal levels of the hormone DHT (dihydrotestosterone). These follicles, found in the frontal hairline and extending into the top and crown of the head, become smaller and produce a hair that is progressively thinner and less pigmented.
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DHT also affects these follicles' growth cycles, causing them to produce shorter and shorter hair until these follicles finally "die." It is at this point that hair production ceases forever in those follicles and microscopic scarring occurs. The hair found at the side and lower back of the head is relatively permanent because the follicles in that area are not sensitive to the effects of DHT; and this is why nearly all male pattern hair loss ends in a similar "pattern," hence the term, 'male pattern baldness.' Because of this odd genetic code, hair growth rates may vary with age, and hair loss typically does not occur on other parts of the body. This is why a man's beard may still be strong and full, while he is losing hair on his scalp.
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