Hair disorder, especially when severe, often profoundly affects the lives of those afflicted. Severe hair loss evokes not only cosmetic concerns but may also evoke feelings of vulnerability (nakedness), loss of self-esteem and alterations in self-image. Each hair follicle produces hair in phases. There is a growing (anagen) phase, which lasts from 2 to 6 years, a resting (catagen) phase which lasts for about 3 months, and finally the shedding of the hair (telogen) phase which allows the follicle to begin pushing a new hair to the surface.

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.

Most modern medical research leans toward the position that a male hormone called dehydrotestosterone (DHT), which is converted from testosterone, binds to sites on hair follicles and is a primary instigator of hair loss. DHT appears to make the follicles go into their "resting" phase faster which in turn starts to cause the hairs produced by those follicles to become thinner and thinner with each growth cycle. Studies show that while balding men don't have higher than average circulating testosterone levels, they do possess above-average amounts of DHT in the scalp follicles.

Genetics and hormones have a part to play in this: each hair follicle appears to have a predetermined number of sites that DHT can bind to. In one study which compared the follicles between hairy and bald human male scalps, the bald scalps had twice as many binding sites for DHT as did their hairy counterparts.

Poor circulation and nutrition can also hamper hair growth. A study of young men diagnosed with male pattern baldness showed that the blood flow to their scalps was on average 2.6 times lower than in a control group. In many individuals the extremities, including the top of the head, are the most difficult places in the body for blood to reach. Follicles which are constantly deprived of blood, and therefore nutrients, cannot produce hair properly.

Male Pattern Baldness
Beginning as early as the late teens or early twenties, by age 35 to 40 two thirds of Caucasian men experience some hair loss. This type of baldness is largely hereditary. Hair becomes finer and does not grow as long as it once did. The hair on the crown of the head begins to thin out and over time there develops a horse-shoe pattern of hair around the sides of the 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.

One plausible theory to explain some of the difference between men and women is based on the angle of follicles and resultant sebum build-up. The angle at which hairs come out of a female scalp allow the sebum (oil produced by the scalp) to "run off" whereas the angle of hairs on a male scalp (straight up) can lead to oil blockage.

Recently, a group of Japanese researcher reported a correlation between excessive sebum in the scalp and hair loss. Excessive sebum often accompanying thinning hair is attributed to an enlargement of the sebaceous gland. They believed excessive sebum causes a high level of 5-alpha reductase, the enzyme which converts testosterone into dihydrotestosterone (DHT), and pore clogging, thus malnutrition of the hair root and a shift into the resting phase.

Although this condition could be hereditary, they believe diet is a more likely cause. The researchers note that Japanese hair was thick and healthy, with a small gland and little scalp oil, until large amounts of animal fat crept into their diet after World War II. This change has led to a significant height increase in the Japanese population, but it has also resulted in more Japanese men losing hair. To some extent, their observation makes sense: problems with greasy hair have often been noted as much as six months to a year prior hair thinning becoming noticeable. However, this might just be one of the symptoms instead of an underlying cause, so more research is needed.

Most doctors agree that if you have a oily scalp with thinning hair, frequent shampooing is advised. shampooing can reduce surface sebum, which contains high levels of testosterone and DHT that may reenter the skin and affect the hair follicle.

Specific foods or vitamins don't regrow hair, although good nutrition is essential for healthy hair.