Male Pattern Hair Loss: Why Do We Lose Hair?
Balding is a normal process that develops to some degree in all men. It is influenced by male sex hormones, called androgens. Hormones are chemical messengers produced by the body that stimulates activity by organs or tissues elsewhere in the body. There also is a strong inherited factor in balding. The trait can be inherited from either the mother's or the father's side of the family. It can affect both men and women, although women with this inherited tendency do not become completely bald.
The process of balding is due to progressive miniaturization of individual hair follicles, which become smaller and have a shorter growth cycle. The hairs consequently become smaller and narrower. The number of hair follicles remains the same, however. There is the same number of hair follicles in the scalp of a bald man as in the scalp of a man with a full head of hair.
There is tremendous variation in the extent to which individuals may lose hair. Some men experience a recession of the front hairline above the temples while retaining hair in the middle, which creates an "M" shape in the hairline above the temples and forehead. Some lose hair on the center of the scalp, which produces a "bald spot" surrounded by hair. Yet others have the recession at the front of their scalp join up with this area to create a larger balding area. Some men develop uniform thinning of the hair over the top of the scalp, with no discernible pattern; this usually progresses to complete baldness.
Under normal circumstances hair growth in each hair follicle occurs in a cycle. There are three main phases of the hair growth cycle; anagen, catagen and telogen with anagen further subdivided into proanagen, mesanagen and metanagen. Anagen is the active growth phase when hair fiber is produced. Proanagen marks initiation of growth with RNA and DNA synthesis in a follicle which then quickly progresses through mesanagen to metanagen and maximum follicle length and girth. In this mature state of proliferation and differentiation the hair follicle consists of a total of eight concentric layers of different cell types and melanogenesis occurs within pigmented hair follicles. Anagen is followed by catagen, a period of controlled regression of the hair follicle. Ultimately the hair follicle enters telogen, when the follicle is in a so-called resting state.
ANAGEN is the longest phase with up to 90% of follicles on a normal human scalp in this active hair growth state at any given time and correspondingly telogen hair follicles comprise up to 10% on the scalp. The average rate of hair fiber growth is around 0.35mm a day but this rate varies depending on the site of the hair follicle and the age and sex of the individual. The length of the anagen growth phase for scalp hair is usually 3-6 years while telogen lasts just 30-90 days and catagen is best estimated at 14-21 days. In many young mammals the anagen growth phase occurs in a wave like pattern across the skin surface, but the hair follicles of humans can run through the normal cycles of growth apparently independently of neighboring follicles.
Early hair loss is usually seen as a receding hairline or thinning spot on the back of the head. If allowed to continue, it may become hereditary male pattern baldness, or MPB, which is properly known as androgenetic alopecia. This condition afflicts approximately half of the male population by the age of 50, and is the cause of the overall thinning most often experienced by women.
In another form, especially seen in women, we may see sudden balding in irregular patches on the scalp known as alopecia areata. It is suspected that in most of these cases, the bodies nervous system may have been injured in some way, causing the affected area to be poorly nourished. [read more] |
