When there is a family history having a genetic predisposition or susceptibility to thinning hair and hair loss, it is commonly known as male or female pattern hair loss. In pattern hair loss, the enzyme 5-Alpha-Reductase (5AR) is primarily responsible for the conversion of the circulating hormone Testosterone into the hormone Di - Hydro - Testosterone (DHT), which starts the process of your losing your hair.

If you are a male and any of the following family members have or had thinning hair or hair loss, you also may experience male pattern hair loss: your father, grandfather, uncle or brother. If you are a female, and any of the following family members have or had thinning hair or hair loss, you also may experience female pattern hair loss: your father, grandfather, uncle or brother or your mother, grandmother, aunt or sister.

Many people are not aware that various kinds of prescription drugs and medications may either cause or contribute to thinning hair and hairloss. This includes various acne treatments, anti-depressants, birth control pills, chemotherapy, drugs which help lower cholesterol, high blood pressure, treating ulcers, arthritis and blood thinners. You may see an extended list of medications which cause hair loss.

Various kinds of health and medical conditions such as hyperthyroidism and lupus can cause thinning hair. Some women experience sudden hair loss at the conclusion of pregnancy or two to three months after discontinuing the use of birth control pills.

It is commonly thought that extended periods of high stress can cause or contribute to hair loss, as stress may increase a constriction of the blood supply to the scalp. Sometimes after surgery, some individuals may experience either temporary or long term hair loss.

Poor diet and nutrition may also contribute to losing one's hair (but not as pattern hair loss). This may include diets high in animal fat (too much red meat / acidity), too much protein, too much fast food or quick weight loss diets.

Androgenetic Alopcia (AGA) - also known as Male or Female pattern hair loss or pattern baldness. This is the most common type of hair loss. This affects approximately 60 million people in America: 40 million males and 20 million females. About 95% of the men and women who lose their hair can attribute their hair thinning and hairloss  to pattern hairloss. This type of hair loss is the result of genetics (ie: heredity). It is widely believed that the genetics of pattern hair loss in men and women are associated with a fairly large number of genes (at least eight genes are already known) interacting in intricate orchestration. This is one reason why there are so many degrees and variations of pattern hair loss among both Men and Women.

Alopecia Areata (AA) - a sudden loss of hair in round irregular patches, where the scalp is not visibly inflamed. This type of hair loss occurs in individuals who have no obvious skin disorders or serious disease. The cause is unknown, but may be related to stress or auto-immune disease. Alopecia Areata may be confined to a few areas of the scalp and is often reversed in a few months. According to the National Alopecia Areata Foundation, an estimated four million men, women and children suffer from this type of hair loss. 

Postpartum Alopecia - a temporary scattered hair loss at the end of pregnancy.

Telogen Efflivium - a premature shedding of hair in the resting or telogen phase, which can result from various causes such as childbirth, shock, side effects of various medications, fever, etc. Some women also experience sudden hair loss when they discontinue use of birth control pills or follow extreme diets too low in protein. The hair loss is usually reversed once the condition is resolved. You can learn more about the three stages of normal hair growth.

Patchy or scattered hair loss due to the use of hot combs (including hot curling irons and straightening irons) or repetitive traction of the hair by pulling or twisting. This type of hair loss could also occur after excessive applications of chemical agents such as relaxers and permanent waves, especially those that use lye-based perms and colorings. This condition is usually reversed once the trauma is stopped.