Reasons for hair loss are not yet fully recognized. Loss of hair can be due to genetic disorders. Medically, continuous loss of hair is known as alopecia.
Hair loss may be for the short duration (less than 3 months), long duration (3 to 24 months), or permanent.
Development of hair takes place in various stages. The starting stage is anagen (meaning growth) stage during which divisions of cell of hair bulb secretes keratinocytes forming various layers of the individual hair shaft. Melanocytes of hair bulb impart color to the hair by the process of pigmentation which involves kazeratinocytes. After the hair has grown to a certain length, it undergoes the degradation stage known as catagen stage. At this stage cell division and pigmentation stops and the hair enters resting stage called telogen. During this stage, existing follicle is replaced by a new follicle (shedding of hair) and a new hair grows to replace the original. At any point of time 80 to 90 percent of the hairs are in anagen stage, 10 to 20 percent are in the telogen stage and rest 1 to 2 percent are in catagen stage.
Loss of hair takes place whenever there is any deviation in the normal processes of telogen or anagen stages. When telogen stage is extended, excessive shedding of hair takes place as a result excessive hair loss is observed, and medically this is termed as telogen effluvium. When anagen stage of hair development fails, then there is a loss of hair. Alopecia areata universalis is a condition of loss of hair occurring due to failure of anagen stage. Failure of anagen stage is considered the most vide spread cause of hair loss. Androgenetic alopecia (male pattern baldness) is the best example of this type of hair loss. It is believed that effects of dihydotestosterone is the cause of failure of anagen stage
There are several reasons and types of hair loss. Hair loss can take place because of natural aging, diseases, injuries, drug and non-drug treatments.
Following is described in brief various conditions of hair loss.
Male and female pattern baldness
Male-pattern baldness is familial and believed to be influenced by levels of hormone. dihydrotestosterone (DHT) is a hormone responsible for loss of hair in male which is made from male hormone testosterone. Genetically prone persons have hair follicles susceptible to DHT and excess level of DHT results in thin hair and loss of hair. Under the effect of DHT, the growth period of hair is shortened and hairs are shorter than normal and this may affect different areas of the scalp
In addition, in is believed that under the influence of DHT, Benign Prostatic Hyperplasia occurs (BPH-innocent growth of prostatic glands in males) and during this period males are prone to loss of hairs.
Female-pattern baldness is not clearly understood. In the post menopausal period baldness and thinning of hair is common in females as the level of estrogen decreases.
Women suffering from polycystic ovarian syndrome and other hormonal disorders possess higher levels testosterone and are at risk of developing facial hairs and thin hairs over the scalp.
This is an autoimmune disorder. In the case of alopecia areata the immune system does not recognize body’s own cells and damages the hair follicles. The hair follicles in this case are not damaged permanently and hair may grow back in short duration. Alopecia areata also accompanies other autoimmune disorders like hyperthyroidism, diabetes and leucoderma.
Permanent damage to the hair follicles is responsible for this condition. Skin disorders like discoid lupus, lichen planus, folliculitis decalvans, frontal fibrosing alopecia, scleroderma can cause this type of hair loss.
Hair loss occurring due to adverse effects of treatments like cancer chemotherapy, immunotherapy and radiotherapy is called Anagen effluvium. While treating rapidly growing cancer cells, these therapies influence all rapidly growing cells of the body, including cells of hair follicle in certain part of body or allover the body.
This temporary condition of hair loss occurs due to various short-lived conditions. Hormonal changes associated with pregnancy, illness of short duration, emotional stress, severe infections, surgery, chronic illness like liver disorders, cancers etc.
Other causes of hair loss are crash diets, malnutrition and deficiency of vitamins. Hair loss can also occur as adverse effect of some drugs. Anti-coagulants, anti-platelets, anti-thrombotics, beta blockers, cholesterol reducing agents etc. can also cause telogen effluvium.