Alopecia Areata Cause
Common Causes of Hair Loss from the Scalp
Non Scarring Alopecias
A brief review of common causes of hair loss in men and women.
Introduction: Hair loss, or alopecia, is a common and often emotionally distressing condition. Genetic predisposition, disease and improper hair care can all contribute to hair loss. They do so by increasing the rate of hair shedding (hair coming out by the root) or by increasing hair fragility leading to hair that can be broken by even minor trauma. Depending on the cause, there are a number of treatments for scalp hair loss with varying degrees of effectiveness and patient satisfaction. This knol will discuss the typical hair cycle, as well as the various types of scalp hair loss and their associated treatments.
Hair CycleWe are all born with about 100, 000 hair follicles on the scalp. In a normal adult, approximately 90-95% of hairs in any given location are actively growing (anagen) and about 5-10% are in a resting state (telogen). Normal scalp hair grows about one-half inch per month. Hairs will remain in a resting state for about three to four months before being shed when a new hair emerges from the base of the follicle and the new hair "pushes" out the old hair. Each day, up to 100 "resting" hairs are shed from the head.[1] The amount of time a hair stays in the growth phase determines its length and the size of the hair bulb (that portion of the follicle which actively produces the hair) determines its diameter. Sometime to help diagnose the type of hair loss that occurs, physicians may perform a "pull test" where a small cluster of hairs is pulled firmly away from the scalp. If hair is dislodged, the roots can be examined to identify what stage of hair development they are in. This can often help establish what type of hair loss is occurring. To determine if the hair itself is damaged, a "tug" test may be performed where hairs are grasped at the base and center then gently tugged. If the hair is fragile or damaged, the hair will often break.
Hormones are important in regulating hair growth. For instance in puberty when hormone levels increase particular androgens such as testosterone change hair diameter and length. For instance, hairs in the beard, chest, and limbs enlarge but hairs in the temple region generally shrink.
A. 
B.
From http://education.vetmed.vt.edu/curriculum/VM8054/Labs/Lab15/Lab15.htm
Figure 1: Diagram of a Hair Follicle
Common Causes of Hair Loss and Their Treatment
Androgenetic alopecia Androgenetic alopecia (AGA) is a very common condition[2] and is due to progressive thinning of the hair caused by certain hormones called androgens. This condition occurs in men and women who have inherited the susceptibility but have normal levels of male hormones. Many affected individuals have family members with AGA. This condition is also known as male pattern baldness or female pattern hair loss. A.
B.
Photos courtesy of V. Price
Figure 2: Androgenetic alopecia in men (A) and women (B).
The condition affects both men and women equally and begins between the ages of 12 and 40 years of age. Approximately half the population expresses some degree of hair loss due to AGA by the age of 50. In androgen-sensitive hair follicles of the scalp, normal levels of hormones cause hair to transform into progressively shorter and smaller diameter hairs with each successive hair cycle. Over time, only fine, miniaturized hairs remain leading to areas of scalp with decreased hair coverage. In men and women, certain patterns of hair loss are characteristic which helps establish the diagnosis. In men, hair loss in frontal/parietal scalp, top of the scalp (vertex) and bitemporal regions are typical. In women, thinning typically occurs on the frontal scalp although the frontal hairline remains intact. In AGA, the hair pull test is typically negative.
A small subset of women with female pattern hair loss may have an underlying hyperandrogen state such as polycystic ovary syndrome that can also cause menstrual irregularities and hirsutism (abnormal hair growth)[3]. Diagnosis of hyperandrogenism requires special hormone blood tests. The goal of AGA treatment is to increase the coverage of the scalp and prevent further hair thinning. In the United States, oral finasteride (1mg per day) and 5% topical minoxidil solution or foam (applied twice per day) are currently the only drugs approved for promoting hair growth in men. A 2% minoxidil solution is approved for treatment of AGA in women (applied twice a day). Both drugs can increase coverage of the scalp by enlarging existing hairs, and both retard further thinning. However, neither drug restores all hair and responses will vary from individual to individual. In addition, neither drug will benefit totally bald individuals. Finasteride limits further hair loss in 70-80% of male patients. When used for at least two years, 66% of men experienced a 10-25% regrowth of hair[4]. Side effects are rare but include decreased libido and erectile dysfunction in 1.8% of recipients. Minoxidil has also been shown to be effective in several studies. For instance, after 2.5 years, 54% and 48% of patients using minoxidil 5% and 2% solutions, respectively, showed increased hair counts[5]. Side effects include rash in 6.5% of patients or growth of unwanted facial hair in 3-5% of women. In general, treatment with either medication is necessary for about 12 months to improved scalp coverage. If either medication is discontinued, all benefits are lost within one year so continued treatment is needed to maintain benefit. Those patients who respond to treatment require treatment indefinitely. Minoxidil and finasteride can be combined to increase hair regrowth.[6] Minoxidil is available over the counter and can be purchased in most drug stores. Finasteride requires a prescription from a physician. When hair thinning is extensive, men and some women may consider hair transplantation, a surgical procedure that involves moving hair from hair-bearing sites of the head (donor site) to the areas of thinned hair (recipient site). Alternatively, surgery may sometime be performed to remove bald areas of scalp altogether (scalp reduction surgery). Surgical treatment can be combined with finasteride or minoxidil to improve results of surgery. Hair addition devices can be attached to existing hair to give the appearance of a fuller head of hair. Hair weaves, hair extensions, hair pieces, toupees, non-surgical hair replacements, partial hair prostheses, or hair wefts are all examples of these types of devices. Devices may consist of human hair, synthetic fiber or a combination of both. In addition to hair addition devices, there are a variety of "cover-up" products that can be applied to the scalp or to hair in the thinned areas to mask visible scalp and create the illusion of thicker and fuller hair.
To learn more about:
- Hair loss in general, see http://www.hairlossexpert.co.uk/
- Hair restoration surgery, see http://www.ishrs.org/
- Hair addition devices, see http://www.ahlc.org/solutions-nons.htm
- Hair "cover-up" products, see http://www.hairtransplantnetwork.com/Hair-Loss-Treatments/thickners.asp
Causes of telogen effluvium include the following:
1. High fever 2. Childbirth 3. Severe infections 4. Major surgery 5. Crash diets, poor nutrition, inadequate protein 6. Severe psychological stress 7. Thyroid abnormalities 8. Medications 9. MalignancyCategories of medications than may cause telogen effluvium include:
1. Anticancer drugs 2. Anticonvulsants 3. Anticoagulants 4. Antigout medications 5. Antithyroid medications 6. Beta-adrenergic blockers 7. Tricyclic antidepressants 8. Oral contraceptivesThe condition is usually self-limited and treatment of the underlying bodily stress generally results in hair regrowth in 1 to 6 months after the underlying condition is corrected.
Alopecia areataAlopecia areata (AA) is an autoimmune disease that affects almost 2% of the US population, including more than five million people in the United States alone[8]. In alopecia areata, the affected hair follicles are mistakenly attacked by a person's own immune system (white blood cells), resulting in the arrest of the hair growth stage. Alopecia areata usually starts with one or more small, round, smooth bald patches on the scalp and can progress to total scalp hair loss (alopecia totalis) or complete body hair loss (alopecia universalis). Any hair-bearing site on the body can be affected by alopecia areata. Hair loss can often occur without any accompanying symptoms. When the pull test is positive at the borders of an affected hair patch, the immune response against hair follicles is actively occurring.
A. Photo courtesy of V. Price
B.
C.
Figure 2: Alopecia areata of the scalp (A-B) or beard region (C) Although AA affects both sexes equally and occurs at all ages, children and young adults are affected most frequently. Patients with early onset (less than 30 years of age) often have other family members with AA (10-42%) and episodes of hair loss may last longer than patients who develop the disease at an older age (more than 30 years of age). Spontaneous hair regrowth and recurrent patchy hair loss is common at all ages and predicting the course of the disease is difficult. Recovery can be complete or partial; when scalp involvement is limited (less then 25% scalp involvement), 90% of patients will have spontaneous regrowth within two years[9]. This group also generally responds well to treatment. Alopecia totalis or alopecia universalis that lasts longer then two years has a low chance of spontaneous regrowth and is less responsive to therapy. The important point is that the potential for regrowth is always there, and the possibility of a recurrence is also always there. Patients with AA are usually otherwise healthy, but autoimmune thyroid disease, vitiligo (loss of skin pigmentation), and atopy (asthma, eczema or hay fever) are more common among AA patients then in the general population. Patients with AA may also develop rows of shallow pits that occur on the surface of fingernails. The presence of severe nail abnormalities, atopy, and onset of extensive hair loss at less than five years of age may mean these patients will have more severe and long lasting disease than others. Patients with AA are treated with anti inflammatory medications such as injected cortisone or hair growth stimulators such as minoxidil. The choice of therapy depends primarily on the patient's age and extent of hair loss (see Table 1). Therapy should be continued until remission occurs or until residual patches of alopecia are concealed by regrown hair which may take months or years. The most common treatment in adults is intralesional injected cortisone. The concentration of cortisone will vary from treatment site, but typically the medication is injected in 0.5 to 1.0cm intervals within the patches of bare scalp. Side effects of treatment may include local pain from the injection, bleeding, persistent redness and small indentations corresponding to the injection sites.
Table 1: Treatment for Patients with Alopecia Areata According to Age and Severity of Condition[10]
Patients 10 years of age
- 5% Topical minoxidil solution, topical glucocorticoid, or both
- Anthralin (short contact)
Patients 10 years of age
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