To understand the mechanisms linked to accelerated hair loss( or alopecia), it is interesting to look at the anatomy and physiology of the hair. The rod is the visible part of the hair; it is composed of three tubular layers nested inside one another.
The medullary canal consists of marrow forming a central, hollow tunnel made of loose cells. The cortex is a thicker portion; it is the body of the hair fiber, giving the hair its strength and elasticity. Cortex cells produce melanin, responsible for the color of the hair.
The cuticle consists of a bark-like waterproof coating that envelopes the cortex in a layer of 6 to 10 adjacent cells arranged like tiles. When hair is bleached, the process causes a destruction of that layer.
The root is the living part of the hair. Implanted into the scalp, the root is contained in a cavity called the hair follicle. It is covered with epithelial ducts and has a bulb at its lower end; the bulb is innervated and irrigated by blood capillaries.
Hair grows for 2-5 years (anagen phase), then prepares for a 2-3 week period of rest and repairs (catagen), and finally it rests in the third phase (telogen phase). In the telogen phase, the follicle is dormant; at the end of this period of 6-7 months, the hair falls out and is replaced by a new one.
Alopecia, or accelerated hair loss, leads to baldness. Androgenetic alopecia is the most common one and affects 70% of men, among whom 20% are still in their twenties. There are other types of alopecia, including acute alopecia generated by stress or chemotherapy, localized alopecia caused by skin problems, and congenital or areata alopecia, which seems to have an auto-immune origin.
Minoxidil or 6-piperine-1-ylpyrimidine-2,4-diamine 3-oxide, is a topical vasodilator drug, and leads to a reduction and often a cessation of hair loss. Some patients even experience regrowth. The molecule opens potassium channels, causing hyperpolarization of cell membranes. The mechanism by which the drug acts on hair loss is not completely understood. Orally, it is used as a remedy against hypertension. One of the best known brands is Rogaine; generic equivalents, while less expensive, can induce the same effects. Side effects are rare and often negligible; the most common is itching of the scalp. Minoxidil is sold in concentrations of 2 and 5%. In trials, better results were obtained with a 5% solution.
Finasteride, N-(1,1-dimethylethyl) -3-oxo(5α, 17β)-4-azaandrost ene-1-carboxamide-17, sold under the brands Proscar or Propécia, is taken orally. This drug is an inhibitor of 5-alpha reductase, an enzyme that converts testosterone to dihydrotestosterone (DHT), which is the active form of testosterone. DHT is responsible for hair loss in androgenic alopecia. The drug is relatively effective, but has side effects such as reduced libido and in some cases causes impotence. The drug, also used for problems related to an abnormal growth of the prostate or prostatic hyperplasia, was removed by some states for generating dramatic side effects in some patients.
The Last Means: The Hair Transplant
The follicular unit consists of a set of hair roots which are generally grouped by numbers of 1,2,3 or 4. Follicular units are taken from the back of the skull or the occipital area. In cases of androgenic alopecia these hairs never fall because they are resistant to DHT. The transplanted hair will maintain this property and will remain permanently. Grafts usually fall, mostly within two weeks following the implantation; however, the follicles remain intact. The hair grows back in 3 months, but the end result will be fully appreciated after a period of 8-12 months.