What causes hair loss?
If you grew up hearing that baldness is caused by vitamin deficiencies, poor circulation to the scalp or too much hat-wearing, you might be surprised to know that all of these theories have been disproved. Also untrue:
- You can tell if you'll lose your hair by looking at your maternal grandfather and uncles - No.
- Forty-year-old men who haven't lost their hair never will - No.
- Brushing your hair 100 strokes each day makes your hair healthier - No.
Experts say that baldness, or alopecia, is primarily caused by a combination of aging, hormonal changes and family history of baldness (on either parent's side). There are generally two types of hair loss:
- Anagen effluvium - Permanent hair loss caused by the destruction of hair follicles
- Telogen effluvium - Temporary hair loss due to transitory damage to the follicles
Anagen effluvium is generally due to internally administered medications, such as chemotherapy agents, that poison the growing hair follicles. Telogen effluvium is due to an increased number of hair follicles entering the resting stage. The most common causes of telogen effluvium are:
- Physical stress - Surgery, illness, anemia, rapid weight change
- Emotional stress - Mental illness, death of a family member
- Thyroid abnormalities
- Medications - High doses of vitamin A (sometimes present in diet supplements), blood pressure medications, gout medications
- Hormonal changes - Pregnancy, birth control pills, menopause
Up to 95 percent of permanent hair loss is due to androgenetic alopecia, a hereditary condition that affects millions of men, women and children. This condition is characterized by what we call pattern baldness. Male pattern baldness generally starts with a receding hairline at the front or thinning of the crown hair and gradually progresses until, in extreme cases, only a thin horseshoe-shaped rim of hair remains at the back and sides of the head. Female pattern baldness, which has received more attention in recent years, refers to general thinning of hair all over the scalp, usually beginning at around age 30 and becoming more noticeable after 40 and particularly after menopause.
Along with advancing age and an inherited tendency to bald early (a more complex link than researchers originally thought), androgenetic alopecia is sped up by an over-abundance of the male hormone dihydrotestosterone (DHT) within the hair follicle. DHT is a highly active form of testosterone, which influences certain aspects of masculine behavior, from aggression to sex drive.
Testosterone is converted to DHT by an enzyme called 5-alpha reductase, which is produced in the prostate, the scalp and various adrenal glands. Over time, DHT causes hair follicles to degrade and shortens their anagen, or active, phase.
Technically, the follicle is still alive and connected to a good blood supply (that's why it can nurture a transplanted follicle that is immune to the effects of DHT), but it will grow smaller and smaller. Some follicles will die, but most will simply shrink in size and produce weaker hairs. The progressively shorter anagen growing cycle means more hairs are shed and remaining hairs become so thin that they cannot survive daily wear and tear, experts say. Hairs in balding areas gradually change from long, coarse, thick, colored hairs into fine, unpigmented, fuzzy hairs.