• Common Causes of Hair Loss

    Just like any medical condition, before a treatment plan can be undertaken, the cause should be known. Hair loss is no different. Before undergoing a hair transplant surgery, the cause of the hair loss should be determined. While the most common cause of hair loss in both men and women is androgenic alopecia, failure to properly diagnose the cause of hair loss can lead to poor long term results or even missing a more serious medical condition.

    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 enzymes 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.

    Cells in the body can only respond to hormones if they have receptors for those hormones. 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 transplant techniques. Hair on the back and sides of the head will not fall out in patients suffering from androgenic alopecia because those areas do not have receptors for DHT. When transplanted to a new site, the hair will not gain DHT receptors and will start to grow as if nothing had happened. While the transplanted hair will not fall out because of DHT effects, the natural hair in that area can continue to fall out because it still has receptors for DHT.

    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 the resting phase of the hair cycle, 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 usually maintaining the anterior hairline. Androgenic alopecia appears to be genetically determined and its development is related to age as well as the presence of the hormones in receptive hairs.

    The exact genetic basis of androgenic alopecia has not been determined. Several theories and genes have been suggested but none definitively proven. 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.