Hair loss in men can be devastating to self-esteem, confidence, and body image. Consequently, hair replacement is a huge industry. However, hair loss can also be a sign of a medical problem.

Significant baldness strikes about 50% of men aged 50 years. By age 70, about 80% of men have the characteristic monk hairline—bald on top with hair only around the temples and back of head.

"Men fear baldness so much because it's a sign of the aging process—that he's getting older and becoming more vulnerable," says William Boss, MD, associate chief of plastic surgery at Hackensack Medical Center. "It's natural for males to think they are invincible, but baldness is a very visible chink in the armor."

Oddly, a completely shaven head—like that of Mr. Clean, Yul Brynner as the King of Siam, and Sean Connery—can be the picture of manly virility. For most men, the dreaded loss of hair starts with a receding hairline and, with time, results in hair that covers only the back of the neck and just over the ears. If balding starts in the teen years, it is usually extensive. Some balding men only call attention to their condition by growing the hair above their ears very long and then combing the scant strands across their glistening domes. Others just wear hairpieces.

So, what causes hair loss? Doctors think a male hormone, androgen, interrupts the natural growth cycle of hair in the front and crown regions of the scalp, but it does not happen without genetic predisposition. "Look to your father and grandfather to get an idea of what your own hair line may do as you age," says Mark Stevens, PhD, professor of psychology at the University of Southern California. "Actually, the most dominant part of your DNA inheritance comes from your mother. So look closely at her brothers and her father for clues about your hairline."

Thomas F. Downham II, MD, in the department of dermatology at Henry Ford Medical Center in Detroit, Michigan, points out, "Don't just jump to the conclusion you have male pattern baldness because you are losing some hair. That hair loss could also be a sign of low serum iron, an early indication of a blood condition. Or it could be caused by the medications you are taking, or it could be a sign hypothyroidism. Of the medical specialists, dermatologists are best suited to evaluate hair loss." Moreover, hair loss can be a side effect from taking certain medicines, like drugs to treat high blood pressure, beta-blockers, and anticancer preparations.

You can also lose a lot of hair during times of intense stress. Being shipped off to a war, losing a job, being hospitalized, or the rigors of divorce court can cause a type of balding.