Hair loss is genetic — but it can be treated

Is hair loss preventable? Is it hereditary?

Our genes do indeed determine how much hair we'll have and how long we'll keep it, says Dr. Denise Burke, a Medford dermatologist.

But just because your father was bald doesn't mean you'll inevitably be hairless, too. Burke says the hair gene has what physicians call "variable expression," which means hair loss may not occur in everybody who gets the gene.

The gene's erratic behavior also means that some people start losing their hair sooner than others. The amount of hair loss can vary, too, but some degree of hair loss is nearly universal among men. Burke says about 96 percent of all men will eventually experience at least some hair thinning in the temples even if they don't lose hair anywhere else.

Men who lose their hair are sensitive to a chemical called DHT, or dihydrotesterone, a by-product of testosterone. Prolonged exposure to DHT causes the hair follicles (the specialized cells that produce the hairs) start to shrink. The hair shafts gradually become thinner and thinner, until they disappear.  

The most common form of hair loss, known as male pattern baldness (or "androgenetic alopecia") is extremely common and it affects more than half of all men. Hair gradually disappears from the top and sides of the head, but a fringe of varying density remains around the ears.

Burke says certain areas of the scalp are more susceptible to the "androgen effect" of DHT and other chemicals. The hair follicles on the back of the scalp and along the margins are not as affected by DHT and therefore not as likely to disappear.

Hair loss can't be prevented, but it can be treated with drugs. Burke says minoxidil (trademarked as Rogaine) stimulates hair growth in about 50 to 55 percent of people who use it. It's applied topically twice a day.

Minoxidil was developed as a medicine to treat high blood pressure. Its ability to promote hair growth was discovered as a side effect. It was originally a prescription medicine, but can now be purchased over the counter.

Another hair loss medicine, finasteride (trademarked as Propecia) is a pill that's taken once a day. Burke says about 48 percent of people who use it will see some regrowth.

Propecia, which is a prescription medicine, works by decreasing DHT, the chemical that causes the hair follicles to shrink. Nobody knows the mechanism that makes Rogaine work, Burke says.

How much hair the drugs produce varies tremendously. Some people grow no more than a thin crop of fine hair; for others, the new growth is thick and dense. Burke says the earlier such products are used, the more likely they are to promote hair growth.

There are surgical treatments for hair loss, too. Physicians can remove parts of the scalp that no longer grow hair and pull forward the areas of scalp that still grow hair.

"It's like a face lift," Burke said, "but it's a scalp lift."

Physicians can also transplant plugs of hair-growing scalp into areas that no longer grow hair.

Many kinds of hair loss are not hereditary.

"Telogen effluvium" is a condition that causes an abnormally large number of hair follicles to enter the resting phase that they normally pass through after a hair falls out in preparation for growing a new hair. The extra shedding usually occurs in connection with illness, thyroid abnormalities, major surgery, medications, or low iron levels.

"Alopecia areata" is a disease that causes smooth, circular patches of hair loss, and in many patients its primary cause is not evident. Some conflicting studies show that alopecia areata occurred after severe emotional stress.

Alopecia areata also tends to run in families. Ten to 50 percent of cases occur in families with a history of this disease. This kind of hair loss has been seen in people with thyroid abnormalities, but it is not believed to be caused by thyroid abnormalities.

"Anagen effluvium" is hair loss in the growing stage. This is the hair loss that's associated with the radiation and chemotherapy treatments given to cancer patients.

With hair loss so common among men, it's tempting to think it must have some purpose, but Burke says no one has been able to find any evolutionary reason why men lose their hair.