"The adult human body averages five million hairs, of which 100,000 to 150,000 are on the scalp. Hair is composed of keratin, the same protein that makes up nails and the outer layer of our skin. The part seen rising out of the skin is called hair shaft or strand. Each strand consist of three layers. The outermost protective layer (cuticle) is thin and colorless. The middle layer, or cortex , is the thicknest. It provides strength, determines your hair color and whether your hair is straight or curly.

Hair color is determined by melanin from your pigment cells. The more pigment granules there are, and the more tightly packed, the darker the hair. Two kinds of melanin contribute to hair color. Eumelanin colors hair brown to black, and an iron-rich pigment, pheomelanin colors it yellow-blonde to red. Whether hair is mousy, brown, brunette or black depends on the type and amount of melanin and how densely it's distributed within the hair. For example, deep-black African hair contains closely packed melanin in the cortex, a few in the cuticle. Very dark European hair, quite apart from having more melanin granules than lighter or blonde hair, has more melanin per granule. When pigment-producing cells cease to function, the result is the uncolored white or gray hair.

In Caucasians, true blonds typically have more hair (about 140,000 hair) than brunette (about 105,000) or redhead (about 90,000).

Below your skin is the hair root which is enclosed by a sack-like structure called the hair follicle. Tiny blood vessels at the base of the follicle provide nourishment. A nearby gland secretes a mixture of fats (called sebum) which keep the hair shiny and waterproof to some extent. At the base of the follicle is the papilla, which is the "hair manufacturing plant." The papilla is fed by the blood-stream which carries nourishment to produce new hair. Male hormones or androgens regulate hair growth. Pubic and axillary (armpit) hair are particularly androgen-sensitive and grow at lower androgen levels than hair on the chest or legs. In boys, most pubic hair is grown by age 15, followed by the development of armpit hair two to three years later. In girls, too, an increase in androgens at puberty triggers growth of pubic and armpit hair. Scalp hair, not directly androgen-responsive, is influenced by local amounts of a testosterone derivative, dihydrotestosterone.

Hair follicles initially form in utero. No new follicles are created after birth, and none are lost in adult life. The first hair to be produced by the fetal hair follicles is Lanugo hair, which is fine, soft, and unpigmented. This is usually shed in about the eighth month of gestation. The first postnatal hair is vellus hair, which is fine, soft, usually unpigmented, and seldom more than 2 cm long. Vellus hair remains on the so-called hairless regions of the body, such as the forehead and balding scalp. At puberty, the vellus hair in some areas is replaced by terminal hair, which is longer, coarser, and pigmented. Growth starts in the pubic region; then the eyelashes and eyebrows become thicker. Axillary hair and male facial hair appear about two years after growth of pubic hair begins. Body hair continues to develop long after puberty, stimulated by male hormones that paradoxically, also cause terminal hair to be replaced by vellus hair when balding begins.

Scalp hair fibers grow from 100,000 to 350,000 follicles which are reported to occupy the human scalp; however, not all the follicles are productive. In each producing follicle, the duration of the hair's life cycle is influenced by age, pathology and a wide variety of physiological factors.[1,2] The life cycle is divided into the anagen (active), catagen (transitional) and telogen (resting) phases.

The anagen phase is the period of active hair growth where protein synthesis and keratinization are continuously occurring. In normal subjects, this phase lasts for up to five years, although longer durations have been documented. The cessation of the anagen phase is characterized by a transitory phase known as catagen. This phase lasts for two to three weeks. Following the catagen phase, the hair enters the telogen or "resting" phase. In normal subjects, telogen hair is retained within the scalp for up to 12 weeks before the emerging new hair dislodges it from its follicle.

During the anagen phase, protein synthesis is the main distinction of the hair bulb. In the telogen phase, the dermal papilla undergoes renewal. It is at this time that structural characteristics can be modified. The new hair should be identical to its predecessor, but with advancing age, and in some pathological states, a strict copy is not maintained. In these circumstances, the hair may become finer and shorter, modifying the esthetic profile. Since these effects occur over several hair cycles, years may elapse before the affected individual recognizes the difference.

Like skin cells, hair grows and is shed regularly. Shedding anywhere from 50 to 100 hairs per day is considered normal. The average rate of growth is about 1/2 inch a month. It is now known that hair grows fastest in the summer, slowest in the winter, speeds up under heat and friction, but slows down when exposed to cold. Hair grows the best between the ages of 15 to 30. But, hair growth begins to wind down sometime between the ages of 40 and 50. Progressive hairloss begins naturally in both sex about age 50, accelerating in the 70s. About 40 percent of Caucasian men lose hair to some extent by age 35."*

What are the different types of hairloss?

Alopecia Universalis is when all or almost all hair on the body is lost (hair on head, eyebrows, eylashes, etc.)

"By far the most common form of hairloss is determined by our genes and hormones: Also known as androgen-dependent, androgenic, or genetic hairloss. 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 hairloss include common baldness, diffuse hairloss, male or female pattern baldness."*

What is the cause of MPB?

"The rate of hair shedding in androgenic alopecia is speeded up by three forces: advancing age, an inherited tendency to bald early, and an over-abundance of the male hormone dihydrotestosterone (DHT) within the hair follicle. DHT is a highly active form of testosterone, which influences many aspects of manly behavior, from sex drive to aggression. The conversion from testosterone to DHT is driven by an enzyme called 5-alpha reductase, which is produced in the prostate, various adrenal glands, and the scalp. Over time, the action of DHT causes the hair follicle to degrade and shortens the anagen phase. Though the follicle is technically still alive and connected to a good blood supply--it can successfully nurture a transplanted follicle which is immune to the effects of DHT--it will grow smaller and smaller. Some follicles will gradually die, but most will simply shrink to the size they were when you were born which produce weaker hairs. With a steadily shorter anagen growing cycle, more hairs are shed, the hairs becoming thinner and thinner until they are too fine to survive daily wear and tear. Balding hair gradually changes from long, thick, coarse, pigmented hair into fine, unpigmented vellus sprouts."*

"Current research also indicates an immunological factor in balding. Basically, the immune system begins to target the hair follicles in the hairloss area. The current theory is that the rise in male hormones such as DHT during puberty INITIATES this process. This is why many drugs which lower male hormone levels do not completely stop and reverse the hairloss process. One other target of treatment is to manipulate the messenger chemicals in the body that tell follicles to initiate anagen and telogen phases. Super Oxide radical is believed to be one of the messenger substances causing hair to enter telogen (resting phase), while nitric oxide is one of the messenger substances causing hair to enter anagen (growth) phase. These treatments use topical treatments to stimulate nitric oxide levels while decreasing Super Oxide Radical levels using Super Oxide Dismutase (SODases). Many of the drugs currently being researched and studied by the FDA are SODases."**

"However, the sebaceous gland attached to it remains the same size. As the hair shafts become smaller, the gland continues to pump out about the same amount of oil. So as your hair thins, you will notice that your hair becomes flatter and oilier.

Other physiological factors might cause hairloss. Recently, a group of Japanese researcher reported a correlation between excessive sebum in the scalp and hairloss. Excessive sebum often accompanying thinning hair is attributed to an enlargement of the sebaceous gland. They believed excessive sebum causes an high level of 5-alpha reductase and pore clogging, thus malnutrition of the hair root.

Although this condition could be hereditary, they believe diet is a more prominent cause. The researchers note that Japanese hair was thick and healthy, with a small gland and little scalp oil, until the occidental habit of consuming 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 since problems with greasy hair have often been noted as much as six months to a year prior to when thinning hair becomes noticeable, but this might be just one of the symptons, not underlying cause, 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."*

*Source: Health Review Magazine, January 1996. All rights reserved. E-mail us!
**Source: Hairloss FAQ, Peter H. Proctor, PhD, MD.