Male alopecia is mostly androgenetic alopecia (AGA), also known as seborrheic alopecia, male pattern baldness, premature baldness, which can develop in both men and women. The main manifestation is progressive hair loss in the frontotemporal area and the top, followed by the formation of high forehead, occipital area is less involved, head skin greasy, flaky, or with itching, the course of the disease is slow, the cause of the disease is not completely understood, the current study shows that it is a hormone-dependent polygenic genetic disease. 1975 study shows that 50% of men will occur at the age of 50 years AGA, with the possibility of occurrence of 70% as age increases. A recent study showed that the age of onset of AGA is mostly concentrated in 20-40 years old, suggesting that it is related to the active adrenal function and increased secretion of androgens during this period, and is associated with family and social exertion. It can be speculated that modern social life leads to significantly earlier age of androgenic alopecia. Since AGA mostly occurs in brain workers such as management, teachers, students, professional technicians, etc., it seriously affects the psychological health of such people and even their marriage and career. Most patients believe that it is related to heredity and there is no medicine to cure it, plus there are many advertisements for various kinds of hair loss treatment, which makes them doubt the efficacy, so that few people seek medical treatment, especially after middle age, they are already married and have children and have a successful career, so they Do not care about the image, just let it be, or even simply shaved bald. However, modern medicine has proved that AGA can be controlled, especially in the early stages of the effect is better, drug treatment side effects are less, can be tolerated. Etiology and pathogenesis 1, androgen action: At a very early stage, domestic and foreign scholars have noticed that castration does not occur in people with AGA, while taking testosterone can aggravate hair loss in genetically susceptible people, and stopping the progress of hair loss with testosterone. This suggests in a way that androgens are related to hair loss. The main androgens in men are testosterone and dihydrotestosterone (DHT), the latter is 5 times stronger than the former. DHT is mostly converted from testosterone under the action of 5α-reductase, while some DHT can be produced directly by the gonads or converted from other forms of androgens. 5α-reductase has two isoenzymes, type I in the sebaceous glands and type II in the gonads and hair follicles in the beard area of the scalp, while type I leads to high sebum secretion and excessive sebum accumulation around the hair follicles, causing inflammation and affecting the growth of the hair follicles. Airoldi found that 5-alpha reductase isoenzymes were more distributed and more active in the external hair root sheath, internal hair root sheath, and hair bulb of the scalp in the occipital, temporal frontal, and parietal areas of the alopecia areata by fluorimetry. Obana et al. found through animal experiments that testosterone can also inhibit hair growth by inducing inhibitory factors in hair papilla cells and growth factors that trigger the production of inhibitors in the hair follicle epithelium. In addition, AGA patients have higher than normal serum levels of another class of hormone dehydroepiandrosterone sulfate (DHEA), and DHEA can inhibit adenylate cyclase activity, making hair follicles smaller. 2, the role of genes: the occurrence and progression of AGA shows obvious genetic, the incidence of different races is not gay suggests the role of genetics. However, the specific genetic variation characteristics are not completely clear, some people speculate that it may be autosomal dominant, more scholars tend to polygenic inheritance. Many scholars believe that polymorphisms in the androgen receptor gene may be closely related to the progression and extent of AGA. In the alopecia area, high expression of androgen receptor genes was found. Functional mutations within or adjacent to the androgen receptor gene can lead to its high expression. It has been demonstrated that genetic variants of the androgen receptor are the main determinants of the occurrence of AGA, and that multiple repeats of the GGN sequence on its first exon may be the main variant feature of receptor gene variants. This is still controversial. 3, the role of blood and cytokines Subscalp blood flow studies show that normal people have 10 times more subscalp blood flow than other parts of the volume, early AGA male alopecia at the subcutaneous blood flow and normal people than the reduction of 2.6 times. The signaling and regulation of hair growth and development by growth factors are mainly manifested as follows: regulation of skin development, which determines the density size and type of hair follicles; effects on cell division in the hair bulb, which determines the characteristics of the hair; effects on the hair growth cycle, which is regulated by complex intercellular signaling and a number of known peptide growth factors. The hair follicle and its surrounding tissues produce specific factors by autocrine and paracrine means that act on hair growth and development and cycle. The hair follicle, when stimulated by testosterone, releases insulin-like growth factor-1, which induces the production of 5α-reductase. 4. Other aspects such as excessive brain use, mental stress, and mental health can trigger or lead to aggravation of AGA, and the mechanism may be directly or indirectly related to androgen and sebaceous gland secretion. Treatment 2.1 5α-reductase inhibitors: 1. Finasteride is the most commonly used Finasteride was initially used to treat benign prostatic hypertrophy, and during the treatment process, it was found that hair grew on the bald scalp of AGA patients, which led to the development of a drug to treat AGA. After oral absorption, it inhibits the conversion of testosterone into DHT and can reduce the concentration of DHT in the blood by more than 60%, and it takes 4 months to be effective and at least 24 months to judge the efficacy. Several studies have shown that it can slow the progression of hair loss and significantly and consistently improve hair growth. Hair growth can be seen with 1mg daily for 3 months or more, not only increasing the number of hairs, but also improving length, diameter and pigmentation. In a study of 508 patients, 32% had moderate to intensive hair regrowth, 34% had mild regrowth, and the rest had stopped progressing. The only significant side effect was loss of libido, with an incidence of 1.8% compared to 1.3% in the placebo group. Sexual desire returned to normal after discontinuation of the drug in all cases. Newer studies have shown a more definite effect in patients under 26 years of age. Gaiya palm extract (serenoa repens) also contains 5α-reductase inhibitor, can be taken orally or topically, the side effect is gynecomastia feminization. 2, minoxidil: minoxidil initially used for the treatment of severe intractable hypertension, clinical findings, taking the drug for more than a month of patients can appear hirsutism, thus discovering its role in hair growth. 1996 FDA approved minoxidil for the treatment of AGA, its mechanism has: can stimulate the proliferation of hair follicle epithelial cells, animal experiments show that it increases the dermal papillae, hair matrices, outer hair root sheath and peri-hair fibroblasts Animal experiments have shown that it can increase the number of synthesis, thus prolonging the hair growth period and promoting the conversion of fine hair to terminal hair; promote angiogenesis and increase local blood supply; open potassium channels and block the inward flow of calcium ions, thus promoting hair growth; upregulation of vascular endothelial growth factor (VEGF) in hair papilla cells. In one study treating AGA with 2% minoxidil, one-third had mild to moderate hair growth at 3 months and 56% had significant improvement in appearance at 12 months. 5% concentration was most effective. In a 5-year clinical trial, 31 patients with AGA were treated with topical application of 2% and 3% minoxidil, and hair regrowth peaked at 1 year of treatment, after which hair growth slowed, and at 4.5 to 5 years, there were still significantly more non-cute hairs present than at the beginning of treatment. The main adverse effect of minoxidil solution is hirsutism, a large-scale safety trial has shown that minoxidil is safe and effective in the treatment of androgenetic alopecia, does not increase cardiovascular events, no significant systemic adverse reactions, some can appear pruritus and scalp flaking, mostly allergic to its solvent propylene glycol, can be replaced by other solvent preparations, or reduce the concentration. It is clinically proven that the shorter the hair loss time and the smaller the area, the better the prognosis. 3.Hair transplantation: For severe and advanced AGA with poor effect of drugs alone, hair transplantation can be considered. Compared to drug treatment, hair transplantation is fast-acting, precise and long-lasting. Non-androgen-sensitive hair follicles from the occipital area can be transplanted to the balding area, which can maintain its original characteristics and continue to grow. You can also consider the transplantation based on the combination of drugs, the effect is better. 4.Other: Not commonly used drugs are: androgen receptor blockers such as fluridil, RU58841, inotrol acetate and other topical drugs. There are also drugs that convert testosterone to estrogen by enhancing aromatase activity such as androstadienone and 17α estradiol, which have more side effects for systemic use and are suitable for topical use. Although the etiology of androgenetic alopecia is complex, its key pathogenesis is related to androgens, especially to testosterone and dihydrotestosterone levels, with the latter acting more obviously, and numerous drugs are basically based on this theory. Please don’t be discouraged if you have androgenetic alopecia, reasonable and timely treatment can completely restore your youthful image and regain your confidence.