The New York City sales manager watched day after day as the side part in her long, dark hair grew wider and wider. 

"My appearance was really important because I was traveling and always meeting a lot of people for my job," said Amy, now 40. "It was really bothering me." 

Amy made an appointment with Dr. Gary Hitzig, a hair-loss specialist in Manhattan who was recommended by her boyfriend. 

"I walked into his office and demanded a transplant," Amy recalled. "I told him I wanted those plugs like my boyfriend, but he talked me out of it. He convinced me that a hair transplant wasn't the right way to go for me. He said women's hair loss is different and should be treated differently." 

Hitzig, who specializes in hair replacement because he lost much of his own hair by the time he was 18, recommended that Amy use minoxidil, a drug sold over the counter as Rogaine. 

Amy used it for a year and says her hair grew back and her thinning problem hasn't returned. Then, when she discussed the problem with her 30-something female friends, she was surprised to learn some knew exactly what she was talking about. 

That's because balding and thinning is not an exclusively male problem at all. Hair loss, in fact, affects as many as one in four women in this country, Hitzig said. That adds up somewhere between 20 million to 30 million women.

For most women who come to him, Hitzig says, he mainly recommends minoxidil. "I'm seeing four or five women a week in my office, and I advise very few to get a transplant," he added. 

Hitzig generally prescribes one or two six-month "cycles" of minoxidil. That seems to cure the problem in most cases, he said. No one knows why women respond this way, because men who use the drug must continue it for a lifetime. 

Larger follicles, more coverage   

Minoxidil works by enlarging miniaturized hair follicles and reversing the miniaturization process, Hitzig said. It prolongs the growth phase of the hair cycle, which allows the hair to become longer and thicker. And with more follicles in the growth phase at the same time, there's greater coverage of the scalp. 

But before you rush out to buy minoxidil, Hitzig advised that "women should see a physician at least once to rule out other reasons for hair thinning or loss." 

These can include thyroid problems, anemia, a side effect of medication, or even alopecia areata, which is an autoimmune condition that causes hair to fall out in clumps. There are three types of alopecia: patchy, which causes small circular areas of hair loss on the scalp; alopecia totalis, which causes complete baldness; and alopecia universalis, which causes loss of all body hair. 

Although many women experience thinning hair in the perimenopausal and menopausal years, the problem is only partially related to hormones, according to Dr. Robert Scheinberg, a San Diego-area dermatologist and a clinical professor at the University of California at San Diego School of Medicine. 

"Thinning hair and balding has more to do with heredity," he said. "Hair falls out because of the way the hair follicle metabolizes testosterone, an inherited trait. Testosterone shortens the life cycle of the hair, so it falls out sooner than it ordinarily would." 

At any given time, about 85 percent of hairs are in the growing phase, and the remainder are in the resting phase, Scheinberg noted. Balding occurs when hair falls out but has no replacement. 

Unlike men who lose hair in one place, women usually experience hair thinning evenly all over their scalp. 

"A woman has to lose about 50 percent of her hair in one area before it becomes cosmetically noticeable," Scheinberg said. "But of course, she notices it before that." 

Unfortunately, taking estrogen will not thicken hair, Hitzig said, and although thinning hair poses no health threat, the psychological fallout can be difficult. 

'Devastating for a woman'   

Lorraine G. noticed about a year ago that, after shampooing, her comb was loaded with much more hair than usual. 

"There are some days I just look at the comb and say, 'What's going on?' " said the 47-year-old Southern Californian woman. "At a certain point I thought, well, should I just shave my head? Maybe I'd look great in a wig, but I'd have to take it off eventually." 

Lorraine feels that "losing hair is a much more devastating thing for a woman than a man." 

She recently began using minoxidil, which is the only medication approved by the FDA for women. 

Medication is not the only way to treat hair loss, however. Creative styling; wigs or hairpieces; hair weaves; bonding (where the hairpiece is glued to the scalp); and transplants all have advantages and disadvantages, Hitzig said, and each person must decide which method is best. 

There also is no shortage of hucksters — especially via the Internet — ready to take money from desperate consumers for worthless products. 

"Everyone believes that what they try initially is working," Hitzig said of remedies other than transplants and minoxidil. "Then about six months later they figure out it really doesn't." 

What to do   

To learn more about women and hair loss, visit the National Alopecia Areata Foundation or the American Hair Loss Council. 

To learn more about minoxidil, visit Pharmacia & Upjohn's Web site.