5-alpha reductase

Related Terms

5-alpha reductase, 5AR, aldactone, alopecia, alopecia areata, androgenetic alopecia, antiandrogen, bald, balding, baldness, brow lift, cimetidine, dermatology, DHT, dihydrotestosterone, facelift, finasteride, follicle, frontal recession, graft, hair extension, hair loss treatment, hair replacement, hair transplant, hirsuitism, loniten, Minoxidil, Propecia, Proscar, receding hair line, Rogaine, scalp extender, scalp flap, scalp lift, scalp reduction, spironolactone, Tagamet, tissue expander, trichotillomania.


Hair restoration is a term that covers a number of methods used to restore hair to balding areas (areas with hair loss). Hair restoration may involve topical, oral, and surgical treatments. These procedures are designed to restore or improve the natural hairline in those who suffer from male pattern baldness and other conditions resulting in hair loss. Baldness refers to excessive hair loss from the scalp and may be the result of inherited traits, certain medications, or an underlying medical condition. Adults as well as children may experience hair loss. The medical term for hair loss is alopecia.
Most hair restoration drugs were developed to treat medical conditions other than hair loss. Manufacturers began testing certain drugs for hair restoration after many patients with other conditions showed increased hair growth and decreased hair loss as side effects of the intended therapy. Through the mid 1970s, most hair restoration procedures involved relocating large grafts of hair or cosmetic procedures which left scars. Since then, hair restoration procedures have been refined.
Increasingly, women as well as men are using medications to treat their hair loss. The variety of drugs available is expanding as the cost becomes more affordable. Several herbal therapies have also been studied such as thyme, lavender and zinc; however, lack of high quality trials prevents making any firm recommendations about these therapies.

Theory / Evidence

About 90% of the hair on most people's scalps is in a two to six-year growth (anagen) stage at any given time. The other 10% is in a two to three-month resting (telogen) phase, after which time it is shed. Most people shed 50 to 150 hairs a day. Once a hair is shed, the growth stage begins again as a new hair from the same follicle replaces the shed hair. New hair grows at a rate of approximately one-half inch each month.
Hair loss may lead to baldness when the rate of shedding exceeds the rate of regrowth, when new hair is thinner than the hair shed, or when hair comes out in patches. Based on scientific evidence, hair loss does not result from poor circulation to the scalp, dandruff, or excessive hat wearing.
Pattern baldness (androgenetic alopecia), the most common type of alopecia, affects roughly one-third of men and women. It is genetic and usually permanent. Hair loss may occur as early the teen years in men, with balding typically characterized by hair loss that begins at the temples and crown. The result may be partial or complete baldness. Women with androgenetic alopecia usually have hair loss limited to thinning at the front, sides or crown. Complete baldness rarely occurs in women. With alopecia areata, baldness usually occurs in small, round, smooth patches. A person may lose only scalp hair or may lose body hair as well; this type of hair loss may be temporary.
Hair loss in all individuals is in part determined by heredity. A person's sensitivity to DHT (dihydrotestosterone), the hormone that shortens the hair life cycle, is genetically determined. DHT is believed to shorten the growth, or anagen, phase of the hair cycle, causing miniaturisation (shrinking) of the follicles, and producing progressively finer hairs. The production of DHT is regulated by an enzyme called 5-alpha reductase (5AR).
In men, the loss starts at puberty and continues with age due to the production of dihydrotestosterone (DHT), the active form of testosterone. The individual hairs become smaller, thinner, and less pigmented. The hair's growth cycle, usually four to six years, becomes shorter until it stops completely. Men see frontal recession and crown (top) thinning.
Hair loss in women usually begins after menopause. The significant hormonal and metabolic changes that accompany this stage of life usually play a role. Women usually do not experience complete baldness. The causes of hair loss in women are complex and are due to both hormonal (DHT) and non-hormonal factors. The loss is more diffuse and involves the back, sides, and top of the scalp with preservation of the frontal hairline. In women, medications to promote hair growth release anti-androgens.
Hair loss during pregnancy is uncommon, but occurs sometimes due to a vitamin or mineral deficiency or hormonal changes. Pregnancy-related hair loss most often occurs several months after delivery. During pregnancy, an increased percentage of hairs are in a growing phase and normal shedding of hair declines. After a woman gives birth, a large number of follicles shed hair at once. Although unsettling, this hair loss is temporary. Hair typically returns to its normal fullness and growth cycle within a few months. Individuals who experience hair loss in patches should consult their doctor.
Other common causes include illness, nutritional deficiencies, stress, medications, injury, high fever, scalp infection, harsh hair-care products, and some hair-styling practices. Cancer treatments, such as chemotherapy and radiation, also may cause hair loss. Some individuals may want hair restoration because of trichotillomania, a condition of compulsive hair pulling.
Several drugs have been approved by the Food and Drug Administration as safe and effective for treatment of hair loss.

Author information

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).


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Hair replacement: Non-surgical hair replacement is an option for those who suffer from significant hair loss and would like to regain the appearance of having a full head of hair without surgery. Examples of products available include semi-permanent attached hairpieces, temporary adhesive-attached hairpieces, and clip attachments.
Hair replacement surgery: This method is usually performed by a licensed physician as an outpatient procedure, and rarely requires a hospital stay. Insurance generally does not cover surgery that is done purely for cosmetic reasons. Surgery to correct hair loss from accidents, burns, disease, or trauma may be reimbursable in whole or in part. It is the patient's responsibility to check with the insurance carrier for information on the degree of coverage.
Hair restoration surgery: Dermatologists and dermatologic surgeons can perform surgery to restore hair and create a natural-looking hairline. It is most commonly used for male pattern baldness. The second most common use is to treat female pattern baldness. Hair restoration can also be used to treat hair loss caused by scarring, burns, irradiation therapy, or past infections as well as to restore hair to the eyebrows, eyelashes, beard, and any other area. Hair restoration surgery may be performed during a cosmetic procedure such as a facelift or brow-lift. New options and techniques have made hair restoration safer and easier. Most procedures are done in an office setting under local anesthesia.
Hair transplants: Hair transplant surgery is based on the principle of donor dominance (hair from healthy donor sites will grow normally when transplanted into balding recipient sites). Hair grows in clusters containing one to five individual hairs called follicular units. Grafting involves removing small strips of the hair-bearing scalp. The harvested strips of hair-bearing scalp are divided into grafts for placement in the balding areas. These grafts may be processed into a variety of different sizes, depending on the patient's specific needs. Very small grafts are useful particularly at the hairline, and can be undetectable when they grow out. Larger grafts containing more hairs are used to obtain greater density behind the hairline. The areas from which the strips are taken are carefully repaired, usually resulting in a very narrow scar easily hidden by overlying hair. Recently, body hairs have been used as donor sources; however, a person's own hair must be used as hair from others will be rejected.
Medications: A variety of medications may be taken for hair loss. Some of these medications may work for women as well as men. Others, however, are restricted in their use to one sex. Aldactone (spironolactone) was originally marketed as a diuretic for patients suffering from congestive heart failure. This medication is a pill that is taken once or twice daily. Women now take the drug because its antiandrogen properties halt and sometimes reverse hair loss. This medication may take many months to show results in women. It also may be more effective in post-menopausal women and may be taken with a hormone replacement pill. Minoxidil (Rogaine) is available with a doctor's prescription to treat androgenic alopecia. Once used to treat high blood pressure, minoxidil is now used to treat hair loss in both men and women. This medication is applied directly to the area of hair loss at least two times a day and typically used for at least four months. Patients who discontinue use of Minoxidil will most likely lose the hair that they have already grown. Minoxidil works by enlarging hair follicles. Another drug, Propecia (finasteride), can be obtained from a medical doctor. This treatment is available by prescription only, and works only in men. This pill must be taken daily to regrow hair. Propecia works by inhibiting high levels of DHT (dihydrotestosterone), a hormone, around hair follicles. High amounts of DHT cause hair follicles to shrink, and hair falls out as a result. Proscar (finasteride) was created to treat benign prostatic hypertrophy, but it is now known to reduce hair loss in men. It is usually taken with Rogaine. This medication is a 5-alpha reductase (5AR) inhibitor. This medicine decreases the body's production of DHT, the chemical responsible for shrinkage of hair follicles. Furthermore, Tagamet (cimetidine) was initially used to treat heartburn and stomach ulcers. Recently, this medication became available over the counter. While primarily used a histamine-blocking agent, it is also an antiandrogen, and thus only works for women. Tagamet has been used to treat hirsuitism (excessive facial hair) and androgenic alopecia in women.
Scalp extenders or tissue expanders: May be used to increase the effectiveness of a scalp reduction. The extender, which acts like a large rubber band, or the expander, which acts like a balloon, is inserted under the scalp for about three to four weeks to stretch the hair-bearing areas. This allows for an even greater reduction in the balding regions. Scalp reduction surgery can be performed alone or in conjunction with a hair transplant.
Scalp lifts and scalp flaps: Surgical procedures that involve rotating larger sections of the hair-bearing scalp to cover bald areas. This is mainly used to treat scarring or during trauma repair.
Scalp reduction: This is a treatment option for patients with balding. It may be used to treat areas of hair loss that develop on the top and/or back of the head. The bald areas are reduced or eliminated by excising (removing) several inches of bald skin, pulling the sides together and suturing (stitching up).