An average human body contains roughly five million hairs, with 100,000-150,000 being on the scalp. Hair follicles are all generated before birth, and remain constant throughout life. Not all follicles become active, and some lose their hair production capacity through time. Active follicles normally go through a life cycle which includes a growth phase, followed by a transitional phase, and then a resting phase. These cycles can be as long as five years and come to an end when the hairs are actively shed. Shedding of anywhere from 50 to 150 hairs per day is normal. Unfortunately, in many people some of the hairs do not grow as long or as thick as did in previous cycles. An estimated 40% of males lose hair to some extent by the age of 35.

The vast majority of cases of hair loss can be attributed to our genes and our hormones, and contrary to popular belief, it is not traced only to the mother’s side. This form of hair loss is termed androgen-dependent, androgenic, or genetic hair loss. It is the largest category of hair loss, or alopecia, to affect both men and women. Other commonly used names for genetic hair loss include common baldness and male or female pattern baldness. While male pattern baldness (MPB) is often characterized by a receding hairline and moderate to extensive loss of hair on the crown, female pattern baldness (FPB) is usually characterized by a generalized modest thinning of hair all over the head.

MPB usually starts at the temples, where the hair gradually recedes to form the shape of an “M”. This hair often becomes finer and does not grow as long as it once did. Next, the hair on the crown of the head begins to thin out and eventually the top points of the “M” meet the thin spot the crown. Over time, a horse-shoe pattern of hair around the sides of the head develops. The remaining hairs in the balding areas usually become finer and grow at a slower rate. Since this type of baldness is largely hereditary, a man can often predict the extent of his future baldness by examining family portraits. Roughly 50% of children with a balding parent of either sex will inherit the dominant baldness gene and eventually display similar characteristics.

FPB usually becomes noticeable around the age of 40, and may progress rapidly after menopause. Female hair loss is often a more generalized thinning, and not contained to an isolated spot on top of the head. Studies show roughly 20 million American women have this type of hair loss. Similar to males, hair follicles simply shut down, with hormones playing some role in the process.