Types of Hair Loss
Male Pattern Baldness
Male pattern balding, the most common type in men, usually starts at the temples and gradually recedes to form an "M" shape. Hair on the top of the head thins. Over time, hair takes on a horseshoe-shaped pattern. Some males have only a receding hairline or bald spots at the crown. Hair remaining in the balding area(s) is long, thick, and pigmented. It then changes into fine, non-pigmented hair that grows at a slow rate. Males losing their hair during the mid-teen years are likely to become completely bald on top of their heads.3
Androgenetic alopecia (AGA) is a major factor in male pattern baldness. AGA is attributed to androgens, hormones that are responsible for male characteristics. AGA has three causal factors: advanced age, an inherited tendency to early baldness, and overabundance of dihydrotestosterone (DHT). DHT, which is derived from testosterone, is the most potent androgen in the hair follicle. Testosterone is metabolized into DHT by 5-alpha-reductase, an enzyme produced in the prostate, adrenal glands, and scalp. DHT (and perhaps other androgens) causes hair follicles to shrink and enter a permanent dormant state. DHT triggers synthesis of transforming growth factor-beta2 (TGF-beta2), which suppresses epithelial cell proliferation and eventually leads to apoptotic cell death.4 TGF-beta2 is directly responsible for significant hair loss on a cellular level. Using combination therapy (with current DHT and androgen inhibitors) to combat the effects of TGF-beta2 may have a significant role in treating hair loss.5
Female Pattern Baldness
Female pattern baldness (or diffused thinning) is caused by aging, genetic susceptibility, and androgens.5 Female pattern baldness usually begins about age 30. It becomes more noticeable by age 40 and can be quite evident following menopause. Female pattern baldness usually causes hair to thin all over the head. It rarely progresses to near or total baldness. Female pattern baldness causes permanent hair loss.
Telogen effluvium is an abnormal loss of hair caused by alteration of a normal hair cycle. In telogen effluvium, a large proportion of hair enters the dormant phase and hair shedding is greater than normal.6 Telogen effluvium can follow a case of flu, emotional stress,7 or can occur after a pregnancy. Hormonal changes in pregnancy can cause increased numbers of hair follicles to remain in a growth phase. After pregnancy, an increased proportion of these hairs enter a dormant phase, a temporary self-correction that increases hair shedding.8 This condition is seen when birth control pills are stopped.9
Chemotherapeutic Hair Loss
Cancer chemotherapy causes hair cells to stop dividing, a usually transient condition.10 Hair can fall out for 3 to 4 months before growing back. When a drug is prescribed, ask your physician if a side effect is hair loss. Side effects of all prescription drugs are listed in the Physicians' Desk Reference. Pharmacists also have this information.
Alopecia areata is a highly unpredictable, autoimmune skin condition that causes loss of scalp hair, facial hair, and hair elsewhere on the body. It affects approximately 1.7% of individuals (over 4.7 million people) in the United States.11 In alopecia areata, affected hair follicles are mistakenly attacked by an individual’s immune system (white blood cells) and the hair growth stage is arrested. Alopecia areata typically begins with one or more small, round, smooth bald patches on the scalp. It can progress to total scalp hair loss (alopecia totalis) or total body hair loss (alopecia universalis).12 Alopecia areata affects males and females of all ages and races. Onset often begins in childhood when it can be emotionally devastating. Alopecia areata is not life-threatening, but is life-altering. Its sudden onset, recurrent episodes, and unpredictable course have profound psychological impact.
Trichotillomania is a psychological disorder (an impulse control disorder). Impulse control disorders are characterized by an uncontrollable urge (or impulse) to harm oneself or others. Trichotillomania patients repetitively pull hair out at the root of the scalp, eyebrows, eyelashes, or chronically scratch or brush their hair. Trichotillomania affects 1 to 2% of the population, primarily children. Girls are more likely to be affected than boys.
Scarring alopecia describes skin scarred by burns, X-ray therapy, skin cancer, or severe injury which results in hair loss.
Other Causes of Hair Loss
Hair loss can occur from damage caused by hair styling processes and products as well as from twisting and pulling hair. Certain skin conditions cause hair loss and baldness. Hair loss can be caused by oral medications, including cholesterol-lowering drugs, Parkinson's medications,13 antiulcer drugs,14 anticoagulants,15 anti-arthritics,16,17 drugs derived from vitamin A,18 anticonvulsants,19 antidepressants,20 beta-blockers, anti-thyroid agents,21 and anabolic steroids.