By far the most common form of hair loss is determined by our genes and hormones: Also known as androgen-dependent, androgenic, or genetic hair loss. It is the largest single type of recognizable alopecia to affect both men and women. It is estimated that around 30% of Caucasian females are affected before menopause. Other commonly used names for genetic hair loss include common baldness, diffuse hair loss, male or female pattern baldness.

Male Pattern Baldness (MPB) is the hair loss most frequently encountered. It usually starts with the hair at the temples, which gradually recedes to form an "M" shape. You also may find your hair is finer and does not grow as long as it once did. The hair on the crown of your head begins to thin out and eventually at the top points of the "M" meet the thinned spot on your crown. Over time, you are left with a horse-shoe pattern of hair around the sides of your head. Any remaining hair in the balding areas usually manifests some miniaturization - it is thinner and grows at a below-normal rate, changing from long, thick, coarse, pigmented hair into fine, unpigmented sprouts.

Female pattern baldness usually begins about age 30, becomes noticeable around age 40, and may be even more noticeable after menopause. Female hair loss is usually an overall thinning -- two hairs where five used to be--rather than a bald area on top of the head, though women may have a receding hairline, too. It's thought that about 20 million American women have such hair loss. As in males, hair follicles simply shut down, with hormones playing some role in the process.

A receding hairline reflects age, but not necessarily great age, since some men start balding quite young. With the spurt in androgen secretion at puberty, the hairline moves back a little in 96 per cent of boys and 80 per cent of girls. Most boys continue to shed hair as they mature and, if baldness runs in the family, lose increasing amounts. By age 35 to 40, two thirds of Caucasian men are noticeably bald. The loss may begin at age 20, then stop, only to start up again a few years later. Since this type of baldness is largely hereditary, a man can usually, although not always, predict the extent of his future baldness by examining family portraits. About 50 per cent of children with a balding parent of either sex will inherit the dominant baldness gene.