Androgenetic Alopecia (AGA) is a condition characterized by a progressive reduction in hair on the top of the head, known as male pattern baldness in men and female pattern baldness in women, and previously known as seborrheic baldness or early baldness. Androgenetic baldness usually appears at puberty and gets progressively worse with age. The prevalence of the disease varies significantly by race, with a higher prevalence in Caucasians and a lower prevalence in Blacks and Yellows.
Domestic epidemiological surveys show that the prevalence of the disease in China is 15.73% to 19.75% in men and 2.73% to 4.69% in women. The disease has a great impact on the quality of life of patients, if early diagnosis and appropriate treatment, part of the patients can be improved.
I. Etiology and pathogenesis
The etiology of androgenetic alopecia is mainly genetic, but the causative gene is not yet clear, androgens play an important role in the development of AGA. In normal human scalp, about 90% of the hair is in the anagen phase, 1% is in the regressive phase and 8% is in the stationary phase. Patients with androgenic alopecia have increased sensitivity of hair follicles on the top of the head to androgens and increased 5α-reductase activity in the scalp, leading to
2. Female androgenetic alopecia: Female AGA symptoms are less severe and manifest as the hair on the top of the head becomes sparse and diffuse
II. Diagnosis and differential diagnosis
Mainly based on medical history and typical clinical manifestations, positive family history is an important reference indicator for diagnosis, and the following auxiliary examinations help in diagnosis.
(1) Hair pulling test: the proportion of hair in the anagen area decreases, <80%, and intermediate hair appears. Do not shampoo hair for at least 24 hours prior to performing this test.
(2) Histopathological examination: Miniaturization of hair follicles, decrease in the ratio of terminal hair/Cui hair, and increase in the ratio of regression and resting hair follicles are seen. Sparse lymphocytic infiltration is sometimes seen around the upper 1/3 part of the hair follicle.
(3) The disease is mainly distinguished from diffuse non-scarring alopecia, including resting alopecia, anagen alopecia, baldness and plucking fetish.
Female patients with symptoms such as seborrhea, severe acne, hirsutism in women, manifestations of male pattern alopecia, irregular menstruation and obesity need to exclude diseases related to hyperandrogenemia or insulin resistance, and should undergo testing of serum sex hormone levels and blood glucose, and B-mode ultrasonography of the abdomen and pelvis. If necessary, thyroid hormone, hemoglobin and anti-nuclear antibody tests should be performed to exclude resting hair loss caused by abnormal thyroid function, anemia or autoimmune disease.
III. Treatment
Since androgenetic alopecia is a process of progressive aggravation, early treatment is emphasized, and the earlier the treatment, the better the results. Treatment methods mainly include internal medication, external medication and hair transplantation, etc. Combination therapy is recommended.
(I) Internal medication
With reasonable medication, hair loss symptoms can be significantly relieved within 3 to 6 months, and new hair can be produced after treatment lasts for 6 to 12 months. However, hair loss treatment is a long-term process and requires continuous medication to achieve more desirable results.
1. Finasteride and its analogues: Finasteride is an oral drug approved by the U.S. Food and Drug Administration and China’s State Food and Drug Administration for the treatment of male androgenic baldness. Usage: 1mg/d orally. Generally, hair loss starts to decrease after 3 months of taking the drug, and hair starts to grow in 6 to 9 months. The best efficacy can be achieved after 1 to 2 years of continuous use; if the efficacy is to be maintained, a longer maintenance treatment is required. After 1 year of treatment, the effective rate reaches 65% to 90, and the effective rate for hair loss in the forehead is lower than that in the parieto-occipital area.
At least 1 year of treatment is recommended, and if there is no significant effect after 1 year, it is recommended to stop the drug. Finasteride is generally well tolerated, with a low incidence of adverse effects. Individual patients may experience decreased libido, impotence, and decreased ejaculation, most of which gradually resolve over the course of treatment and may subside after a few days or weeks if treatment is discontinued. The finasteride analogue tadalafil has also been reported to treat male androgenetic baldness. Finasteride or tadalostamide at 2.5 mg daily has also been reported to be effective for some women with androgenetic baldness.
2. Spironolactone: It is mainly used for female patients. It can reduce the production of testosterone by the adrenal glands, and also has an inhibitory effect on the binding of DHT to androgen receptors. The usage is 40-200mg/d, which can make some patients’ symptoms improve. The main adverse effects include decreased libido, breast tenderness, and increased urination. The drug is not suitable for the treatment of male patients. Attention to blood potassium concentration is required during treatment. The recommended course of treatment is at least 1 year.
3.Cyproterone: It mainly contains cyproterone 100mg and ethinyl estradiol 30μg, which has strong anti-androgenic effect and is used for female alopecia patients with combined acne and hirsutism, 1 tablet daily, taken on day 5-24 of menstrual cycle. It is contraindicated in patients with hepatic or renal insufficiency and in minors. The main adverse reactions are reduced libido, weight gain, etc.
4, flutamide: can inhibit the production of DHT, dosage: 250mg, 3 times a day, for more than 5 months. The adverse effects of this drug are breast pain, impotence, decreased libido, etc. Therefore, it is not recommended for male patients. Some people report better efficacy than spironolactone, but the drug is not used as the drug of choice.
5, adjuvant therapeutic drugs: Cimetidine has a weak anti-androgenic effect and can compete with DHT for androgen receptors. Dosage: 300mg, 3 to 5 times daily for more than 5 months. Adverse effects are breast pain, impotence, and decreased libido are not recommended for male patients.
Other adjuvant drugs are zinc preparations, cysteine, biotin and folic acid.
(II) Topical drugs
Topical drugs represented by minoxidil are effective for androgenetic alopecia. Topical drugs combined with oral drugs can improve the efficacy.
1, minoxidil: clinically there are 2% and 5% two kinds of concentration dose, usage for twice a day, the dosage is about 1.0 ~ 1.5ml each time. topical minoxidil treatment of androgenetic alopecia average onset of action for 12 weeks, the use of time recommended for more than six months, both men and women can use, the efficiency of up to 50% ~ 85%, to light to moderate hair loss better. If the efficacy is to be maintained, a longer period of maintenance treatment is required. Common adverse events are contact dermatitis and hirsutism.
2.Other topical medications: A study has been conducted to treat male androgenetic baldness with topical 1% finasteride gel and oral finasteride (1mg/d) for 6 months, and the results were similar for both groups, suggesting that topical finasteride gel can also be used to treat androgenetic baldness. Topical cyclosporine has also been reported to be effective for partial androgenetic baldness.
(iii) Physical therapy
In a randomized double-blind study, a 655 nm laser was used to irradiate the scalp in the balding area for 26 weeks, and the results showed that laser irradiation significantly promoted the growth of hair in men with androgenetic baldness.
(iv) Hair transplantation
Hair follicles from congenitally androgen-insensitive areas (usually occipital) are isolated and transplanted to the balding area. The suppressed hair follicles can be kept alive for a long time. In recent years, with the continuous improvement of hair transplantation technology, the hair transplantation technology of separating hair embryos by follicular units has become more and more mature. Generally the hair starts to grow again after 2 to 3 months after transplantation, and the hair loss after transplantation is only temporary.
Indications are mainly for androgenic baldness of grade IV or less, hair loss has stabilized after medication, dense occipital hair, and sufficient hair sources available for transplantation. Contraindications include suffering from serious internal diseases, hair in the donor area is too thin and of too poor quality, etc. Before and after hair transplantation, oral or topical medications are usually required to maintain the growth of non-transplanted hairs in the balding area.