Five Medical Causes for Hair Loss

Hair thinning and hair loss is a common problem experienced by women of all ages and can be detrimental to body image and self-identity. There are many causes of hair loss and hair thinning, and different causes may lead to different patterns of hair problems. In order to understand why this happens, it is helpful to first understand the hair growth cycle. The hair growth cycle consists of several phases, ultimately resulting in the growth of a strand of hair. Growth cycles are important because any interference in one or more stages can impede or prevent the hair from growing, or lead to premature hair loss. Hair thinning can have an immense psychological impact and may be a sign of underlying disease, making it an important issue for health care providers.

Hair Growth Cycles

Hair growth occurs in 3 different phases: anagen, catagen, and telogen. The majority of hair is in the anagen phase, which can last from two to eight years. Most people’s hair grows about six inches per year! Anagen is the main growth phase, resulting in elongation and thickening of the hair. Next, the hair enters the catagen, or transition phase for 2-3 weeks, where the hair follicle begins to shrink. Lastly, the hair enters the telogen cycle which lasts around three months, and the hair stops growing and “rests.”  

Normal Hair Loss

According to the American Academy of Dermatology, most people lose an average of 50 to 100 hairs from their scalp per day.^[1] If you wash your hair, as many as 250 strands can fall out. In fact, many women normally begin having a decrease in hair density and hair diameter around the age of 35, sometimes sooner.^[2] However, there are some warning signs to be aware of that could mean you are losing more hair than normal. If you wake up in the morning and your pillow is smothered in hairs (more than usual), this could mean you are losing hair. Another sign may be a significant increase in hairs left in your comb or brush after combing your hair, or large clumps in your fingers when you run your hands through your hair. Read on for information about five medical causes of hair thinning.

Female Pattern Hair Loss 

Female Pattern Hair Loss (FPHL) affects over 32% of women over the age of 20, making it the most common cause of diffuse hair thinning in women.^[3] In this condition, women usually complain of a widening middle part with increased hair shedding. Similar to male pattern hair loss, which is strongly associated with genetics, FPHL can be a hereditary condition.^[1] Several factors may contribute to this condition, including higher levels of male hormones such as dihydrotestosterone (DHT), lower levels of estrogen, and insulin resistance. Although many women with FPHL have higher than normal levels of the male hormone DHT, some women with FPHL have perfectly normal DHT levels. Estrogen is believed to be protective against FPHL, so women with lower estrogen levels may be at a higher risk for this condition.^[4] Topical treatments such as minoxidil are frequently recommended for women and minoxidil effectively prolongs the hair growth phase and even thickens the hair. There are other treatment options available, such as anti-androgen treatments that may be beneficial in some women with FPHL.^[5]

Telogen Effluvium (Stress Induced Alopecia)

Telogen effluvium (TE) results from a hair cycle abnormality, where more hairs are falling out than growing in. It is unknown how many people are actually affected by this condition because the diagnosis can be difficult.^[6] After a stressful event, many of the hairs that were in a growth phase convert to a resting phase. Hair in a resting phase typically lasts 3-6 months before they fall out and begin a new growth stage. For this reason, the hair loss occurs about 3-6 months after some form of stressful or traumatic life event. Other scenarios, such as a low functioning thyroid gland, crash diets, and certain medications can also result in TE. In many cases, there is often no identifiable inciting event.^[9] This condition typically clears up spontaneously. 

Alopecia Areata

Alopecia areata (AA) is a hair disorder characterized by the sudden onset of round patches of hair loss, revealing a smooth scalp underneath. This condition may occur in up to 2% of Americans by the time they are 50 years old, affecting men and women equally. Alopecia areata is believed to be an autoimmune disease where the body destroys its own hairs. It is also associated with other autoimmune conditions, such as thyroid disease and vitiligo. Often, other family members have or have had alopecia areata. There is no known permanent cure for this disease. Many patients are treated with topical and systemic steroids and can achieve good control.^[10]

Scarring Alopecia

Scarring alopecia encompasses a diverse group of progressive and permanent hair loss disorders. These conditions can be caused by the destruction of the hair follicle from inflammation, can result from an inflammatory process of the scalp skin, or can be due to physical injury or trauma to the scalp. Often the cause is unknown. In general, these conditions are characterized by replacement of hair follicles with fibrous scar tissue.  Some of the hair loss disorders that fall into this category are lupus erythematosus, lichen planopilaris, frontal fibrosing alopecia, and central centrifugal cicatricial alopecia (CCCA).^[11]  

• Lupus erythematosus occurs when the body develops an autoimmune response against the skin. Lupus can appear in several forms that can lead to hair loss. In some cases, the hair loss appears in only on areas of the scalp. In other cases, lupus can affect the entire scalp leading to hair thinning all over.^[12]  
• Lichen planopilaris (LPP) most commonly affects women in their 50s-60s and hair loss typically begins at the crown of the head, forming small and irregular interconnected patches of hair loss.^[13] One variant of LPP called frontal fibrosing alopecia (FFA), results in a characteristic band-like zone of hair loss along the frontal scalp, and it can also affect the eyebrows.^[14]
• Central centrifugal cicatricial alopecia (CCCA) affects primarily women with naturally darker skin and begins with a patch of scarring hair loss at the crown of the head, with progressive hair loss to the sides of the scalp.^[15] CCCA often also causes itching and tenderness.  

The key to treatment in most scarring alopecias is to prevent permanent hair loss, using medications like steroids or immunosuppressants.^[10] A dermatologist can help you discuss treatment possibilities if you are diagnosed with one of these conditions. Diagnosis often involves sampling a piece of skin from the scalp with a biopsy. 

Medication Induced Hair Loss

Many medications can interfere with the normal growth of hair. Diagnosis can be difficult and is best proven when hair starts to regrow after stopping the suspected drug.^[16] The most common form of drug-induced hair loss is telogen effluvium (TE), and it can occur with anti-thyroid medications, some oral contraception pills, and anti-cancer drugs, especially taxane-based chemotherapy agents.^[17,18] In some rare instances chemotherapy agents can lead to permanent alopecia, which has been reported in treatments with busulphan, cyclophosphamide, cisplatin, and paclitaxel.^{[19,20] [21]}