Androgenic Alopecia (AGA), also known as male or female pattern hair loss, is an X-linked genetic condition and one of the most common forms of hair loss. According to the National Institutes of Health, AGA affects an estimated 50 million men and 30 million women in the United States . The condition is so common in men that it is often accepted as being normal. Male AGA occurs in a highly predictable pattern, preferentially affecting the temples, the mid frontal scalp and the crown. Recession of the temporal hairline is not as common in women. The typical pattern in females is a diffuse reduction in hair density over the crown, with widening of the central part-line. Thinning hair may even extend to the side of the scalp. In both sexes, the hair in the back of the scalp is spared. AGA affects all races, with increased prevalence occurring in Caucasian males. AGA affects roughly 30% of men by age 30 and greater than 50% by the age of 50. Fifty-seven percent of women over age 80 are affected with pattern hair loss. In women, hair loss is more likely after menopause . Although often occurring in healthy individuals, AGA has been associated with other more serious conditions such as coronary artery disease, hypertension, diabetes, enlargement of the prostate gland in men, and polycystic ovarian syndrome in women.
Hair growth begins at the hair follicle under the skin and occurs in cycles. About 90% of hairs are normally in the active growth phase (called anagen) which lasts approximately 1000 days in men and 2 to 5 years longer in women. On average, about 50-100 hairs are normally shed every day (telogen phase) .
The hair loss problem also occurs at the follicular level. A variety of genetic factors are likely to play a role in the development of AGA. Environmental factors may also contribute to pattern hair loss but are these are largely unknown. There is a family tendency towards AGA and the condition is believed to involve multiple genes. Variations in one gene in particular, called the AR (androgen receptor gene) have been verified in scientific studies. Variations (called polymorphisms) in the AR gene located on the X chromosome were found in 98.1% of young bald men and 92.3% of older balding men . Other genes are likely to contribute to the development of the disease, and research is underway to identify them.
Polymorphism of the AR gene results in an increased level of sensitivity to a hormone (or androgen) called dihydrotestosterone (DHT). The binding of DHT to the androgen receptor within the hair follicle results in the miniaturization of the hair. Essentially, androgenic alopecia is the conversion of healthy, thick terminal hairs to thin microscopic vellus hairs. Hair follicle miniaturization is the histological hallmark of AGA . The effects of DHT also shorten the hair growth cycle and prolong the hair loss or shedding cycle, therefore reducing the overall number of hairs on the scalp. Such follicular changes are "site specific," and research supports the notion that AGA is dependent on intrinsic factors within each follicle. This explains why hair follicles in the back of the scalp are not prone to loss, while other hairs are. Balding and non-balding regions of the scalp also have different numbers of androgen receptors and varying amounts of DHT which is associated with the geographical pattern of hair loss . An enzyme known as 5-alpha reductase has also been implicated in pattern hair loss. This enzyme is present in the body tissues and serum, and is responsible for converting testosterone to dihydrotestosterone. Normal circulating testosterone may be excessively converted to DHT, or the hair follicle may be abnormally sensitive to DHT, resulting in pattern hair loss .
Hair transplantation surgery exploits the fact that hairs from the back (occipital) scalp are genetically resistant to androgenic alopecia. In fact, transplantation studies reveal that weak scalp hairs from the crown which are transplanted to the forearm continue to miniaturize at the same rate as original neighboring hairs in the crown. Conversely, when occipital scalp hairs are transplanted to the crown they continue to maintain resistance to hair loss . Essentially, the hairs identified as suitable donor grafts are permanent. Hair restoration patient's can expect to keep their grafted hair for a lifetime. Non-transplanted or "native" hair can continue to miniaturize over time. The degree of progression of one's hair loss varies from person-to-person and is dependent upon his or her genetic predisposition to the condition. In general, the earlier the onset of alopecia, the more severe it will be. Fortunately, there are now many treatment options available to slow or even halt the androgenic alopecia process.
There are currently two FDA approved medications for the treatment of AGA: topical minoxidil (Rogaine®) and oral finasteride (Propecia®). Both medications may prevent further hair loss, but can only partially reverse balding. Both medications require indefinite use to maintain results. Minoxidil is available in 2% and 5% topical solutions and is to be applied to the scalp twice daily. Cosmetically acceptable hair growth is seen in about one third of cases . When beginning minoxidil, a temporary effluvium (or shedding) may occur within the first 2 to 8 weeks. Minor side effects such as scalp itching, dandruff and redness may occur. Foam formulations without propylene glycol cause fewer side effects. Maximal response to minoxidil is seen in the first six months of treatment. Regression of results occurs after 3 months of stopping minoxidil .
Finasteride (Propecia®) is potent 5-alpha reductase inhibitor, reducing the conversion of testosterone to DHT. Finasteride is available in a 1 mg prescription tablet. Adverse side effects including sexual dysfunction (decreased sex drive and erectile dysfunction) are uncommon and most often resolve without discontinuing treatment . Side effects occur in less than 1% of men taking the medication. Finasteride lowers DHT levels in the scalp and serum and promotes the conversion of hair follicles to the anagen (active growth) phase. This medication is effective in preventing further hair loss and increasing hair counts. In studies, hair loss on the temples is not improved, although the crown and frontal hair counts are increased. Finasteride must be used indefinitely to maintain a response .
Viviscal professional is a dietary supplement offered in physician offices. This supplement offers superb nutritional benefits to the scalp and hair follicles, nourishing thinning hair and promiting existing hair growth. Ingredients include Vitamin C, Calcium, Biotin, AminoMar Marine Complex (Shark Cartilage and Oyster Powder Extract), Apple (fruit) Extract, L-Cystine and L-Methionine. It is recommend taking 1 tablet twice daily for a minimum of 3-6 months with water after food. Viviscal should be used to supplement a healthy, balanced diet.
 "Androgenetic alopecia," March 2019. [Online]. Available: https://ghr.nlm.nih.gov/condition/androgenetic-alopecia. [Accessed 27 March 2019].
 E. Perera and R. Sinclair, "Androgenetic Alopecia," in Textbook of Trichology, 2014, pp. 1-12.
 J. Janis, "Hair Transplantation," in Essentials of Plastic Surgery, St. Loius, MO, Quality Medical Publishing, Inc., 2007, pp. 780-787.
 W. Cranwell and R. Sinclair, "Male Androgenetic Alopecia," Feb 2016. [Online]. Available: www.ncbi.nlm.nih.gov/books/NBK2278957/#NBK278957_pubdet_. [Accessed 22 Feb 2019].