Androgenic alopecia (AGA), also known as androgenetic alopecia or pattern hair loss, is a genetically determined, progressive loss of hair from the scalp and occurs in both men and women in specific patterns. Men with this condition (male pattern baldness), can begin suffering hair loss as early as their teens or early 20s.

In men, hair is usually lost in a well-defined pattern, beginning above both temples and is usually referred to as male-pattern baldness. Over time, the hairline recedes to form a characteristic ‘M’ shape. Hair also thins near the top of the head, often progressing to partial or complete baldness.

The pattern of hair loss in women differs from men (female pattern hair loss). Women with this condition, don’t experience noticeable thinning as early and they tend to develop a general thinning over the entire scalp, widening of the midline partition and extensive hair loss at the crown. Androgenic alopecia in women rarely leads to total baldness. A variety of genetic and environmental factors likely play a role in causing this condition.

Frequency

AGA is a common disorder that affects roughly 50% of men and perhaps as many women older than 40 years. The incidence of AGA increases greatly in women following menopause.

Race

The incidence and the severity of AGA tend to be highest in whites, second highest in Asians and African Americans, and lowest in Native Americans and Eskimos.

Age

Almost all patients with AGA begin to develop it before the age of 40 years.

Causes

A variety of genetic and environmental factors play a role in causing androgenic alopecia. Many factors still remain unknown to this date.

DHT Hormone

Researchers have determined that AGA is related to hormones called androgens, particularly an androgen called dihydrotestosterone (DHT). DHT is believed to shorten the growth phase (anagen) of the hair cycle, from a usual duration of 3–6 years to just weeks or months. This occurs together with the miniaturisation of hair follicles and progressively produces fewer and finer hair. The production of DHT is regulated by an enzyme called 5-alpha reductase. Androgens are important for normal male sexual development before birth and during puberty. Androgens also have other important functions in both males and females, such as regulating hair growth and sex drive.

There are three types of alpha-reductase receptor isoenzymes, and type I and type II are significant in the treatment of AGA. Type I is located in the skin, including the sebaceous glands and hair follicles, and type II is located in the inner root sheath of hair follicles in the scalp, face, chest, genitals, and prostate gland. Some of the hair follicles are smaller and more sensitive to androgen. The pattern in which the hair loss occurs is genetically predetermined by the distribution of these smaller hair follicles.

Role of Genetics

Several genes play a role in AGA. One gene, in particular, The AR gene has been confirmed in scientific studies to play a part in AGA. The AR gene provides instructions for making a protein called an androgen receptor. Androgen receptors allow the body to respond appropriately to DHT and other androgens. Studies suggest that variations in the AR gene lead to increased activity of androgen receptors in hair follicles.

Recently, two more genes have been identified including PAX1/FOXA2 and HDAC9.

Polycystic Ovarian Syndrome

A few women present with male pattern hair loss because they have excessive levels of androgens as well as genetic predisposition. These women also tend to suffer from acne, irregular menses and excessive facial and body hair. These symptoms are characteristic of polycystic ovarian syndrome (PCOS) although the majority of women with PCOS may not experience this kind of hair loss. Less often, congenital adrenal hyperplasia may be responsible.

Role of other medical conditions

Researchers continue to investigate the connection between AGA and other medical conditions, such as coronary heart disease and prostate cancer in men and polycystic ovary syndrome in women. They believe that some of these disorders may be associated with elevated androgen levels, which may help explain why they tend to occur with androgen-related hair loss.

Other hormonal, environmental, and genetic factors that have not been identified also may be involved.

Role of vitamin D receptors

Some studies have shown that there is a lack in functional vitamin D receptors which may lead to a defect in the cyclic regeneration of hair follicles, leading to the development of AGA although further studies are required.

Role of Oxidative Stress

The study, on males aged 18 to 30 years, found higher total oxidant levels and oxidative stress index values in patients, all of whom had early-onset AGA, than in healthy controls.

Inheritance

The inheritance pattern of AGA is unclear because multiple genetic and environmental factors are likely to be involved. This condition tends to cluster in families, and having a close relative with patterned hair loss appears to be a risk factor for developing the condition.

Features

Signs of androgenic alopecia include the following:

Gradual onset.
Increased hair shedding.
Hair Miniaturisation: Transition in the involved areas from large, thick, pigmented terminal hair to thinner, shorter, indeterminate hair and finally to short, wispy, non-pigmented vellus hair
End result can be an area of total baldness; this area varies from patient to patient and is usually most marked at the vertex

Hair miniaturisation

Unlike other areas of the body, hair on the scalp to grow in tufts of 3–4. In AGA, the tufts progressively lose hair. Eventually, when all the hair in the tuft are gone, bald scalp appears between the hair.

Males

Men note a gradual recession of the frontal hairline early in the process.
Hair is lost in a well-defined pattern, beginning above both temples. Over time, the hairline recedes to form a characteristic “M” shape.
Hair also thins at the crown (near the top of the head), often progressing to partial or complete baldness.

Females

Hair generally is lost diffusely over the crown; this produces a gradual thinning of the hair rather than an area of marked baldness; the part is widest anteriorly
The frontal hairline is usually preserved in women
A bitemporal recession occurs rarely in women.

Prognosis

The prognosis of AGA is unknown. Some patients progress to the point where they lose almost all of the hair on the scalp. Others have a patterned or nonpatterned thinning but retain a considerable number of scalp hair. Women with AGA usually show thinning of the crown rather than developing truly bald areas.

An increase in benign prostatic hypertrophy has also been associated with androgenic alopecia.

A study by Sanke et al indicated that early androgenic alopecia (i.e. prior to age 30 years) in males is the phenotypic equivalent of polycystic ovarian syndrome (PCOS) and that these males may be at risk of developing complications found in association with PCOS, such as obesity, metabolic syndrome, insulin resistance, cardiovascular disease, and infertility.

When to consult a skin specialist

Consult a skin specialist if you notice shedding of hair, receding hairline or thinning of hair. Starting treatment early can help in preventing extensive hair loss. Usually, a person suffering from AGA tends to try various home remedies and other natural treatments and the hairline recedes permanently due to lack of proper diagnosis and treatment so it is important to start the appropriate treatment as soon as possible for the best outcome.

Treatment

Only 2 drugs have been approved by the US-FDA (US Food and Drug Administration) for treatment of androgenic alopecia. They are minoxidil and finasteride. To know more about the treatment of AGA, check out Treating AGA for Men and Women.

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