Like the cure for cancer, those new treatments aren’t nearly ready for prime time. But they’re coming, promises George Cotsarelis, MD, director of the Hair and Scalp Clinic at the University of Pennsylvania, Philadelphia.
“In the last 5 to 7 years there has been a boom in the understanding of hair loss,” Cotsarelis tells WebMD. “We’ve made great strides at the level of basic research. Now the question is how we can convert these findings into clinical benefits. Those kinds of leaps really take decades.”
The great leap would be to grow new hair on bald heads. But smaller steps aren’t that far away.
Why do we care about a cure for baldness? Look around you. Hair loss is extremely common, it usually happens when the normal process of hair growth gets disrupted.
What We Know About Hair
“The hair is real. It’s the head that’s a fake.”
Until it’s gone, hair is easy to take for granted. But a close look reveals the hair follicle to be one of the most interesting organs of the body. It’s most unusual feature: It is self-regenerating.
Hair follicles live just below the top layer of the skin. You have them all over your body except, fortunately, on your lips, palms, and soles.
At the base of the follicle is the hair bulb, where wildly growing matrix cells become hair.
A little farther up the follicle is the mysterious feature called the bulge. That’s where follicle stem cells live. When they get the right set of chemical signals, these self-renewing cells divide. They don’t divide like normal cells, in which both halves become new cells that keep splitting and developing. Only one half of the follicle stem cell does that. The other half becomes a new stem cell, and stays put for future regeneration.
Hair growth goes through several distinct stages:
Anagen. The growth phase of hair. An unknown signal tells follicle stem cells to do their thing. Next, the permanent part of the follicle — the dermal papilla — gives the “go” signal to hair matrix cells. Those cells grow wildly and become pigmented, creating a new hair shaft. At any given time, 90% of hair cells are in this stage.
Exogen. The new hair shaft pushes the old, dead hair shaft out of the skin. The old hair falls out.
Anagen finished. The new hair extends beyond the surface of the skin and keeps growing. The hair shaft fully matures.
Catagen. The lower two-thirds of the follicle shrivels up and is destroyed. The dermal papilla remains attached to the regressing follicle.
Telogen. The withered follicle rests. It waits for a signal telling it to start all over again.
Losing hair is part of a normal cycle of growth and replacement. Hair follicles go through the growth and resting cycle in a nonsynchronized fashion. But sometimes things go wrong.
Common Hair Loss Problems: Androgenetic Alopecia
Most of us, when we think of hair loss, think about aging men. Nearly all men eventually get that receding M-shaped hairline and thinning hair on the top of the head, also known as male pattern baldness. It’s called androgenetic alopecia, and it’s caused by a by-product of testosterone called DHT.
Aging women have a similar problem. Their hair gets thin, although it’s not clear that this is necessarily caused by sex hormones.
What is clear is that the same thing happens in aging men and women. Hair follicles get smaller. The anagen stage of hair growth gets shorter, and the resting (telogen) stage gets longer. The result: Thin, very short hairs — and many follicles empty of hair shafts.
Why is this pattern of hair loss only in the front and on top? That’s where hormone-sensitive follicles live. The follicles on the sides and back of the head aren’t affected by DHT and usually stay healthy.
The name is fancy — telogen effluvium — but all it means is increased hair shedding. Lots of hair shedding. For various reasons, many hair follicles enter the exogen stage all at once.
The good news here is that hair lost this way almost always grows back in a few months.
Cancer cells grow wildly. Chemotherapy takes advantage of this by killing off cells with out-of-control growth. Unfortunately, there’s one kind of normal cell that grows like this: Hair matrix cells.
Chemotherapy forces growing follicles into the catagen stage. The hair shaft doesn’t develop properly, so the hair breaks and falls out.
The good news is that when chemotherapy is over, the follicles regenerate. Healthy, new hair grows again. The bad news is that, in the short term, chemotherapy causes near total hair loss.
Sometimes a person’s immune system attacks the cells of the growing hair bulb. This autoimmune condition is called alopecia areata.
Just as in chemotherapy, hair follicles are forced into the catagen phase. Hairs break and fall out, usually in patches scattered across the scalp.
Sometimes the immune system attacks only the hair bulb. In this case, the hair follicles regenerate when the immune system is brought under control.