There are several types and causes of alopecia or hair loss. Hair loss may occur as a natural part of aging, due to a disease, injury or due to drugs and medications. The causes of alopecia or hair loss include:-
Male-pattern baldness commonly runs in families and may be influenced by levels of hormones. A hormone dihydrotestosterone (DHT) is made from the male hormone testosterone.
In genetically susceptible individuals the hair follicles are exceptionally sensitive to this hormone DHT. Excess DHT leads to thinning and falling of hair. The hair grows for shorter duration and the length of the hair is also shorter than usual. At a given time different areas of the scalp may be affected.
The cause of female-pattern baldness is not very clear. Baldness and thinning of hair is common among women after menopause as the levels of female hormones decline.
In addition women with polycystic ovarian syndrome and other hormonal disorders with higher levels of male sex hormones, there is a risk of excessive facial hair and thinning of hair over the scalp.
This type of hair loss is commonly seen as an autoimmune disease. The immune system is the body’s natural defence system that fights foreign microbes and invaders in the body. Autoimmune diseases are those where the immune system fails to recognize the body’s own cells and tissues and attacks them.
In the case of alopecia areata the immune system damages the hair follicles instead. The hair follicles however are not permanently damaged and hair may grow back in a few months.
Alopecia areata is seen in persons with other autoimmune conditions such as hyperthyroidism or overactive thyroid disease, diabetes and vitiligo.
This type of alopecia is also seen in persons with Down’s syndrome. Genes also predispose a person to alopecia areata.
This condition is caused by permanent damage to the hair follicles. Some skin conditions like lichen planus, discoid lupus, scleroderma, folliculitis decalvans and frontal fibrosing alopecia are causative factors that lead to scarring alopecia.
These disorders commonly cause skin changes, scars, rashes, rough patches over skin etc that leads to loss of hair follicles and loss of hair in particular areas.
This type of hair loss is most commonly caused by drugs like cancer chemotherapy, immunotherapy and radiotherapy. These therapies affect all the rapidly growing cells in the body while they target the rapidly growing cancer cells. Hair follicle cells are one of the cells that are affected by anti cancer drugs and radiation therapy. There may be severe hair loss of scalp, body, eyebrows etc.
This is a temporary form of hair loss that is seen due to various transient changes. One of the common causes is due to hormonal changes associated with pregnancy. Emotional stress, short term illness, operation, severe infections, chronic illness like liver disease, cancers etc are also causes of this type of hair loss.
Malnutrition, crash diets, lack of important nutrients in diet, use of certain drugs like blood clotting medications, beta blockers (for control of blood pressure) etc. are also responsible for telogen effluvium.