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Common Causes of Hair Loss

There are many causes of hair loss. The first step in any treatment plan for hair loss is determining the cause of the hair loss. If a patient undertakes treatment for baldness without first determining the cause, the patient may worsen the condition or overlook a more serious related medical condition. Therefore, the first step in treating baldness is consultation with a physician who has experience in diagnosing and treating hair loss. During the initial consultation with patients, if the cause of a patient's hair loss is not obvious, Dr. Verret will often ask patients to consult with a dermatologist for further work up before undertaking any type of treatment.

Androgenetic Alopecia (Androgenic Alopecia, Male Pattern Baldness, or Female Pattern Baldness)

The most common cause of hair loss, or alopecia, is often referred to as male patterned baldness.  More appropriately, this condition is termed androgenic alopecia or androgenetic alopecia as it can effect women as well as men.  The exact prevalence of androgenic alopecia is unknown. Several studies have reported a greater than 95% incidence in Caucasian men. The incidence increases with age and shows ethnic differences. Estimates have said that 25% of men aged 25 years have some degree of clinically apparent androgenic alopecia and over 40% of men will develop androgenic alopecia at some point in their life.  Androgenic alopecia appears to effect Caucasians most often, followed by East Indians, Asians, and Africans.

The development of androgenic alopecia is dependent on several factors including endocrine and genetic factors but is ultimately due to the effect of androgens, such as testosterone and its byproducts, on hair follicles. In the body, testosterone is broken down into dihydrotestosterone by an enzyme called 5-alpha reductase. Testosterone is also broken down by another set of enzymes called the aromatase enzyme into estradiol and androstenedione. Therefore, an excess of 5-alpha reductase or a deficiency of aromatase can lead to excess dihydrotestosterone(DHT) production. Testosterone influences axillary and public hair growth, whereas DHT affects beard growth and scalp hair, areas which show androgenic alopecia.

In order to be effected by any hormone, a cell must have a receptor on the outside of the cell which is able to connect with that hormone. In the case of the scalp, hair on the top and crown of the head have receptors for DHT while hair on the back and sides of the scalp do not. This knowledge serves as the basis for current hair restoration transplant techniques. Because they do not have DHT receptors, hair on the back and sides of the head will not fall out in patients suffering from androgenic alopecia. When transplanted to a new site, the hair will not gain DHT receptors and will start to grow as if nothing had happened. The transplanted follicle will not be susceptible to DHT that the native hair was.

Androgenic alopecia results from progressive shortening of the anagen cycle with resultant decreased time for hair growth.  The hair will transform from a thick pigmented hair to a fine, colorless, almost invisible hair. The length of time in telogen increases leading to a reduction in total hair density.

Hair loss usually begins with the frontoparietal scalp and then the vertex.  Female-pattern baldness is similar but more diffuse, without complete baldness and maintaining the anterior hairline. Androgenic alopecia appears to be genetically determined and its development is related to age and presence of hormones and the corresponding receptors.

The exact genetic basis of androgenic alopecia has not been determined. Several theories and genes have been suggested but none have been definitely proven. It appears that several genes are responsible for androgenic alopecia. The risk of developing androgenic alopecia increases with a family history in a patient’s father, mother, or maternal grandfather.

Diagnosis is fairly easy given an appropriate history and hair loss pattern and no further testing is generally done. For female patients with evidence of androgen hormone excess, such as inappropriate hair growth in other areas, further testing may be necessary.

Alopecia Areata

The second most common form of alopecia is alopecia areata.  This form of hair loss results in rapid loss of hair in circular or oval patches.  It can progress to encompass the whole scalp, which is termed alopecia totalis, or the entire body, alopecia universalis. It may be episodic or persistent.  There is no definite reason why alopecia areata develops, but there is a genetic predisposition, and popular opinion favors an autoimmune disorder.  Alopecia areata only affects 0.1% of people and equally effects men and women.  Diagnosis is made by microscopic examination of a scalp biopsy in the effected area.

Alopecia areata will generally resolve within six months to a year. Should it persist for longer, the chance of recovery is minimal. The condition will recur in approximately one third of patients. Medical conditions including thyroid abnormalities, vitiligo, and pernicious anemia can accompany alopecia areata. In addition to diagnosing and treating any accompanying medical conditions, medications can be used to treat the hair loss. These medications include steroids and other immunomodulators. Topical, subcutaneous injections, or system medications may be used alone or in combination. One study even suggested hypnotherapy as a successful treatment for alopecia areata. Unfortunately some patients end up resorting to hairpieces or other methods of covering the hair loss because of severe cases not responsive to therapy.

Telogen Effluvium

Approximately 3 months after surgery, childbirth, crash dieting, and other stressful events, hair can enter an extended resting cycle referred to as telogen effluvium.  Usually <50% of the scalp is affected and recovery is complete once the triggering event is resolved. Full recovery take takes six months or longer to occur.


A wide range of medications can cause hair loss.  The most widely known are chemotherapy drugs but other more common drugs including blood thinners and Vitamin A can cause hair loss.  After taking the medications, hair growth is abruptly interrupted and growing hairs are shed after 1-4 weeks.  This form of hair loss rapidly affects 80-90% of the scalp but complete recovery can be expected once the medication is stopped. The most common offenders are some blood pressure medications and blood thinners though there are many others which can cause hair loss.


The most common cause of childhood alopecia is trichotillomania. It is an impulsive disorder in which the patient must pull their hair. Onset is in the early teens. Treatment relies on counseling, behavior modification techniques, and hypnosis. Once the behavior is stopped, the hair will generally regrow as long as scarring has not occurred.

Fungal Infections

Fungal infections of the scalp can cause hair loss in prepubertal patients. Diagnosis of fungal infection is made with a potassium hydroxide slide under a microscope or culture of the fungus which can take quite some time. Once the diagnosis is made, antifungal medications either by mouth and/or applied to the scalp are used to treat the infections.

Nutritional Deficiencies

Nutritional deficiencies can present as hair loss. Generalized malnutrition, zinc deficiency, and iron deficiency are the most common deficiencies causing hair loss. The loss is generalized over the entire body. Once the deficiency is corrected, the loss will generally resolve.

Underlying Disease

Hair loss may occur as part of an underlying disease. Many diseases are associated with hair loss including lupus, diabetes, syphilis, sarcoidosis, lichen planus follicularis, and thyroid disorders. A small patch of hair loss may indicate a skin cancer such as a basal cell carcinoma, squamous cell carcinoma, or other skin cancer. Since hair loss may be an early sign of a disease, it is important to find the cause so that it can be treated. Often once the underlying disease is treated, the hair loss will subside.


Areas of hair which are traumatized can result in hair loss. Hot oil hair treatments or chemicals used in permanents may cause inflammation (swelling) of the hair follicle which can result in scarring and hair loss. Trauma such as cuts, scrapes, or burns can result in permanent hair loss if the underlying follicle is damaged. Surgical excision of the scarred area or hair transplant surgery can be undertaken to correct the cosmetic deformity.

Pulling Hair

Finally, tightly pulling hair can cause hair loss.  People who wear pigtails, cornrows, or use tight hair rollers can pull the hair and cause traction alopecia.  If the pulling is stopped before scarring of the scalp develops, the hair will grow back normally. However, scarring can cause permanent hair loss.

androgenetic alopecia
androgenic alopecia

Dr. D.J. Verret is board certified by the American Board of Otolaryngology, Head & Neck Surgery, is a member of the prestigious International Society of Hair Restoration Surgeons and the American Academy of Facial Plastic & Reconstructive Surgery, and a clinical assistant professor at the University of Texas Southwestern Medical Center. His hair restoration center focusses on natural and long lasting results for people suffering from hair loss. For hair restoration, hair transplants, Dallas hair loss treatments, eyebrow restoration, eyebrow transplants, treatment for male pattern baldness, and treatment for female pattern baldness, consider Dr. Verret. Common misspellings of Dr. Verret's name include Verrett, Verrette, Varret, Verette, Veret, Varratte, Verette, Verrett, and Ferret. Click here for our disclaimer and terms of use.