A normal adult has about 5 million hair out of which 1,00, 000 are present on the scalp. Hair provides a protective covering to the skin and helps in heat trapping. Since the objective of this web site is to providing information on hair loss, we are mainly concerned about the cosmetic and aesthetic aspect of the hair loss and hair loss restoration.
To understand the reasons of hair loss, and hair loss restoration or medical treatment options, it is important for you to know about the basic structure of hair. Knowledge of growth cycle of hair in the normal course and relating it to the altered state (state of increased hair loss) helps you in understanding the difference in hair loss restoration treatments for men and hair loss restoration treatments in women.
A Hair is basically composed of a structural protein called keratin which is also a constituent of our nails and the outer layer of our skin.
Each strand of hair consists of three layers:
- Innermost core known as medulla found only in mature thick hair
- The middle layer or the cortex, the main body of the hair which besides providing the color and texture; provides strength to hair
- The outermost color less layer or cuticle, the main function of which is to protects the cortex.
Formation of hair
If you see below the surface of the skin, the root of hair is enclosed within a hair follicle. The hair follicle is a separate entity within the skin which is formed and maintained through the interaction of dermal and epidermal components. Each hair follicle has an Outer Root Sheath (ORS) which is distinct from other epidermal components of the hair follicle in being continuous with the epidermis. At the base of the follicle, there is a pear shaped structure known as the dermal papilla (DP). DP is the precursor of a hair follicle. DP cells interact with adult epidermis to induce the development of new hair follicles through the process of division, elongation and differentiation. The dermal papilla is connected to the blood capillaries to derive nourishment for emergence of new hair.
The hair follicle together with the sebaceous glands and sheaths is a complete histological and physiological unit.
Under normal circumstances hair growth in each hair follicle follows a well structured cycle. There are three main phases of the hair growth cycle:
1) Anagen - Growth Phase
2) Catagen - Transitional phase
3) Telogen - Resting Phase
Anagan : It is the growth phase during which the hair is actively growing. The growth phase for scalp hair is about 2-6 years, and of total hair about 85% hair are in this phase at any given time.
Catagen : After the Anagen phase, the hairs enter into a Catagen phase which lasts about 30 to 60 days. During this phase the dermal papilla condenses and cells of the follicle stop growing. During this phase a follicle shrinks to about 1/6 its normal length.
Telogen : At this phase the dermal papilla becomes isolated in the dermal area and the hair still lies in the follicle but can be easily pulled out by combing or brushing. (The normal hair loss). And if the old fiber has not already fallen out, it is pushed out by the new hair fiber growing underneath. This phase lasts for about 2 to 3 weeks and of total hair, around 10-15% are in this phase at any given time.
Biology of Hair Loss
The dermal papilla is the most important structure in a hair follicle which is responsible for hair-growth as well as hair loss. Research has shown that dermal papilla contains receptors for male hormones called as androgens. Androgens play a major role in regulating hair-growth. Studies have shown that males have more androgenic receptors in their follicles as compared to females.
DHT the root cause of hair loss
Though male hormones or androgens are present in greater amounts in men than the women, it is the metabolism of androgens which is main cause of hair loss both in men and women.
The metabolism of androgen involves an enzyme called 5 alpha reductase which combines with the hormone (testosterone) to form the DHT (Dihydro-testosterone). DHT is a natural metabolite of our body.
Proper nutrition is critical for the maintenance of the hair. When DHT gets into the hairfollicles and roots (dermal papilla), it prevents necessary proteins, vitamins and minerals from providing nourishment needed to sustain life in the hairs of those follicles. Consequently, hair follicles are reproduced at a much slower rate. This shortens their growing stage (anagen phase) and or lengthens their resting stage (telogen phase) of the follicle. DHT also causes hair follicle to shrink and get progressively smaller and finer. This process is known as miniaturization and causes the hair to ultimately fall. DHT is responsible for 95% of hair loss.
The cause of increased hair loss
Some individuals both men and women are genetically pre-disposed to produce more DHT than the normal individuals. DHT also creates a wax-like substance around the hair roots. It is this accumulation of DHT inside the hair follicles and roots which is one of the primary causes of male and female pattern hair loss.
Blocking the synthesis of DHT at molecular level forms the basis for the treatment of MPHL ( male pattern hair loss) and FPHL ( female pattern hair loss). There are many natural DHT blockers and a number of drugs which are used for medical hair restoration. But in severe cases of hair loss, surgical hair restoration is the only option left.