In humans, some of the skin appendages are hairs. These skin appendages are made of a protein called keratin. On the average, there are over one hundred thousand strands of hair on the head. Normal daily hair loss is about 100 to 150.
Each strand of hair includes two parts:
1- Hair shaft which is located outside the skin and it is observable
2- Hair follicle, which is located in the skin and it is not observable. It has a bag shaped structure that is responsible for producing hair.
Types of hair:
- VELLUS HAIRS
Vellus hairs are short hairs of a centimeter or two long. A vellus hair contains little or no pigment, and thus, is colorless. They are not cosmetically important.
- TERMINAL HAIRS
Terminal hairs are long hairs that grow on the scalp and in many people on the body. They are cosmetically important
- INTERMEDIATE HAIRS
An intermediate hair shows the characteristics of both vellus hairs and terminal hairs.
Hair growth cycle
Each hair follicle lives in a cycle consisting of a long period of growth followed by a relatively short period of rest. During the rest period the hair is still attached to the hair follicle, but it is not growing. After the resting phase the hair is shed and a newer hair begins to grow, thus, starting a new hair growth cycle.There is a genetic predisposition of each hair follicle to follow a particular pattern of growth and rest. Hair follicles are programmed to stop producing hair and spend more time in the resting stage with the progression of age.
The growth cycle of a hair consists of 3 stages:
- ANAGEN (GROWING) STAGE
Approximately 90-85% of hair follicles are in this stage. The anagen stage for the hair follicles in the scalp typically lasts about 3 to 5 years.
- CATAGEN (INTERMEDIATE) STAGE
Approximately 5-3% of hair follicles are in this stage . At the end of the growth period, hair follicles prepare themselves for the resting phase. This transition period of a hair follicle from growth to rest is called the catagen stage. This stage of the hair growth cycle usually lasts about 1 to 2 weeks or so. During the catagen phase the deeper portions of the hair follicles start to collapse.
- TELOGEN (RESTING or SHEDDING) STAGE
This is the resting period of a hair follicle. It is usually 3 to 4 months in length and at the end of this period older hairs that have finished their life will fall out and newer hairs will begin to grow.
The growing (anagen) phase constitutes about 90% (1000 days or more) of the growth cycle of a hair follicle, while intermediate (catagen phase; 10 days) and shedding (telogen phase; 100 days) phases constitute only 10% of it. That is, at a given time, about 10% of hair follicles are in the intermediate and shedding phases; thus, not growing. These hair follicles, however, are randomly distributed over the scalp, so that no bald spots are seen.
Common patterns of hair loss:
1 - Men pattern hair loss (androgenic alopecia):
It is a kind of hair loss that occurs due to an underlying susceptibility of hair follicles to androgenic miniaturization. It is the most common cause of hair loss . Genetic factors play a role in androgenic alopecia. Hair loss starts in both sides of the temple and extends in M shaped form. Localized hair loss occurs at the top of the head. Usually, 30% of men over 30 years and 50% of men over 50 (related to the male hormone) suffer from hair loss.
Men hair loss treatment:
Minoxidil and Finasteride are known as two kinds of medications used to treat baldness androgenetic approved by the United States Food and Drug Administration. These drugs are most effective when they are consumed immediately and in the early stages of hair loss. These medications are required to be used for long term and usually for lifelong in order to be effective. Unfortunately, the current treatment of androgenic alopecia is not very effective.
2.Currently, androgenetic method is considered as the only method for definite cure of baldness all around the world.
Women pattern hair loss (androgenic alopecia in women):
This type of hair loss is hereditary. In this type of hair loss, the first sign is sparseness of hair on the scalp that gradually expands. In women baldness, usually hair line remains fully intact.
Treatment of women pattern hair loss:
1 - Medication:
Oral finasteride, topical spironolactone and Minoxidil are usually used for treatment. The effectiveness of these medications requires long-term and sometimes a lifelong consumptions. However, unfortunately, they are not effective in many cases. Currently, this method is the only useful androgenetic method for definite cure of baldness all around the world.
FUT is the best method in hair restoration surgery in the world. In this method, a strip of scalp (called Hair Bank) is removed under local anesthesia, the wound is then sutured back together in a short time by a team of trained technicians using a microscope. This piece of scalp tissue is then cut in to small pieces of tissue (2 to 4 hair follicular unit )called grafts which are then transplanted back in to the thinning area of the patient's head by subtle tools in depth of 4 mm from scalp. It should be mentioned that this method uses very fine sutures and does not leave a linear scar. Moreover, linear scar in the donor area, will be covered completely by the patient's hair around the linear scar. A short time after hair transplant, the linear scar could not be recognized.
Follicular unit extraction (FIT) or (FUE) is a technique for removing follicular units from the donor area in patients with small or limited areas of hair loss. It uses a knife called “punch” to remove the units in a scattered array from the donor area (Hair Bank) to put it in the hair loss area. The advantage of this method is that there is no need to stitch in the hair bank. The disadvantages of this method are damaging to the isolated hair follicles and inability to cover extensive baldness.
In cases of inappropriate donor hair supply, BHT (Body Hair Transplantation) allows harvesting of additional grafts from different parts of body to be used as the Hair Bank. FIT method is used to extract hair from the hair bank to the hair loss area. This method is suitable for people with weak hair banks hair in which hairs of other parts of the body should be used to cover the planting area.