The most common cause of hair loss in both men and women is rooted in a genetic predisposition. Called androgenic alopecia, it is known as male-pattern baldness in men and female-pattern hair loss in women (alopecia is the scientific term for baldness). According to the American Hair Loss Council, genetics accounts for 95 percent of all cases of hair loss in this country.
Baldness results from a combination of genetic factors and levels of testosterone (a hormone produced by the adrenal gland in both sexes and also by the testes in men). If hormone levels are right, then the hair follicles will express their genetic destiny by growing for shorter periods and producing finer hairs. In men, who have higher levels of testosterone than women, this eventually results in a bald scalp at the crown of the head and a horseshoe-shaped fringe of hair remaining on the sides. In women, the hair thins all over the scalp; the hairline does not recede. This type of hair loss doesn't usually show up in women until menopause; until then, estrogen tends to counteract the effects of testosterone.
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