Baldness is the partial or complete lack of hair growth. This happens in both males and females. Among males, however, gradual baldness may start any time after puberty by recession at the temple hairline and crown thinning. The action of the male hormone, testosterone, on genetically predisposed follicles causes a degenerative change in their hair production capability. Bald patches on the heads of men or women may be due to localized follicle disease such as ring worm and acne (Acne vulgaris), or to other conditions affecting the general health.
Male pattern baldness and female pattern baldness, or androgenetic alopecia, is an inherited trait. It results in too high a concentration of the hormone dihydrotestosterone (DHT) in the blood. The DHT builds up in the scalp and damages the hair-producing follicles, which eventually die. DHT is produced when a chemical in the body converts androgen to DHT.
Around 40 million men and 30 million women in the USA suffer from baldness. Collectively, they spend more than $1 billion a year on shampoos, hair pieces, lotions, pills and follicle transplants (hair transplants: $800 million, with each transplant costing from $3,000 to $20,000; hair systems, also known as toupees and hairpieces: $250 million annually; medical therapies: $225 million; vitamins and nutritional supplements: $60 million.