Hair loss is the bane of middle-aged men’s existence and a source of great embarrassment and discomfort for many women. Its medical name is androgenic alopecia, and it affects about 50 million men and 30 million women in the United States. Although effective treatments for baldness are expensive and imperfect, the science behind the condition is well understood, and it looks better, less expensive treatments are on the way.
Humans have hair everywhere on their bodies except their palms, soles, and lips. It consists of dead keratin cells produced in follicles in the skin. There are 100,000 follicles on top of the head.
The follicle extends up to the surface of the skin like a small tunnel. The base of the follicle contains the papilla, filled with capillaries that nourish the hair. The papilla is surrounded by a bulb of living hair cells that reproduce every 23-72 hours, faster than any other cells in the body.
The follicle is enveloped by an outer and an inner sheath. The sheaths meat at a small oil-secreting gland, sometimes accompanied by a scent gland, at the base of the follicle. A muscle below the gland can cause the hair to spring up and stimulate the gland.
The oil produced by the gland is vital to conditioning the hair. Oil production accelerates during puberty but then slows as the body ages. Men secrete more hair oil than women.
Hair is made up mainly of an inner cortex of keratinous dead hair cells surrounded by a cuticle of tightly overlapping scales. It’s the cortex that mainly gives hair its color.
The hair growth cycle goes through 3 stages.
- Anagen- This is a phase lasting 2-6 years in which hair is actively growing. The cells at the base of the follicle are reproducing quickly and the old hair is being pushed out. During anagen, the hair typically grows 1 cm. every month or so.
- Catagen- This is a 2-3 week period of transitional hair growth. About 3% of hairs are in this stage at a given time. During this stage, the base of the hair hardens as the outer sheath shrinks.
- Telogen- Here hair enters a dormant phase lasting 2-3 months, after which the old hair falls out and the cycle begins again. About 6-8% of hairs are in this state at any time. The hair on legs, arms, eyelashes, and eyebrows has a shorter growth cycle than that on the head and spends more time in telogen, which is why it tends to be shorter.
At any given time, 90% of the hair on the human head is growing. On average, a person will lose 50-100 hairs per day as a result of this normal cycle. The lifecycle of the follicles is influenced by such factors as age, disease, chemotherapy, and more. And if the cycle is interrupted at any step, hair loss may result.
Androgenic alopecia proceeds in a characteristic “M-shaped” formation for men, receding at the top of the forehead first while leaving hair on the sides. Although the full range of genetic and environmental factors that predispose individuals to baldness are not fully known, researchers have linked this type of baldness to the hormones called androgens.
The particular androgen most linked to baldness is called dihydrotestosterone. Androgens regulate hair growth and sex drive for both men and women and play a particular role in the development of male sexuality. In the normal hair growth cycle, increased androgen production can lead to a shorter hair cycle and the production of shorter, thinner hairs.
The exact response of hair follicles to changes in androgen production seems to vary with the follicle’s location on the body. Although it is likely that more than one gene plays a role in the production of androgen, only the one called AR has been isolated at this point. AR provides the body with instructions for regulating androgens.
Men with pattern baldness typically have different hormonal makeup than men who don’t. That includes higher levels of free testosterone and free androgen. These hormonal differences cause hair to spend more time in the dormant telogen stage.
The M-shape characteristic of male-pattern baldness derives from the fact that follicles on different parts of the head respond differently to hormones and thus produce hair at different rates. It is unknown why female baldness follows a different pattern. Call one of our counselors today at 205-352-9141.