Why do some people go bald and some people don't?

The growth and shedding of hair are mainly controlled by the growth period of hair itself, but also influenced by race, endocrine status, disease, mental state, gender, age, season and other factors. (1) Race: Racial difference is an obvious influencing factor. People of different races not only have different hair colors, but also have different hair quantity and growth conditions. Baldness is common in Europe, less in China and even less among Indians. (2) Heredity: In the same family, the growth of hair is often roughly the same. Male baldness is closely related to heredity. (3) Endocrine: Androgen can directly act on hair follicles, leading to male baldness. People who lack androgen stimulation (such as eunuchs) will not have this phenomenon. Estrogen has the function of antagonizing androgen, so women seldom go bald before menopause. In addition, when thyroid hormone is insufficient, hair is scarce; When adrenal function is low, hair decreases; Hypofunction of the anterior pituitary gland can lead to complete baldness. (4) Mental state: nervousness, fear and anxiety can obviously increase hair loss. It is reported that a condemned man once lost 1000 hairs every day after being sentenced. (5) Vitamins: Long-term vitamin A deficiency can lead to thinning hair; Vitamin B2 deficiency will increase sebum overflow and make hair fall off easily. Vitamin B6 deficiency can lead to abnormal sebum secretion, hair whitening and poor growth. Oral contraceptives can speed up metabolism and consume more vitamin B6, which may be related to diffuse hair loss in some women. Deficiency of pantothenic acid (also called vitamin B3) will make hair turn white and grow poorly; Lack of biotin (also known as vitamin H2) can make hair fall off. Inositol belongs to vitamin B family, which can prevent hair from falling off. P-aminobenzoic acid also belongs to B vitamins, which can protect hair color and maintain normal hair growth. (6) Trace elements: Some scholars have observed the changes of trace elements such as zinc, iron, molybdenum, calcium, lead, magnesium, manganese and selenium in hair, and found that zinc, copper, iron and manganese in patients with alopecia decreased significantly, while calcium, magnesium and selenium increased significantly, but there was no difference in trace element values in patients with atypical alopecia. Copper deficiency will affect the absorption and utilization of iron, and poor iron metabolism will not only cause anemia, mental excitement and other symptoms, but also affect the formation of keratinization, which may interfere with cystine's participation in keratin composition, thus affecting hair growth and becoming a promoting factor for alopecia areata. In addition, copper deficiency will also affect the keratinization process of hair, thus affecting hair growth; Calcium plays a role by combining with calmodulin, and high calcium concentration may change the immune regulation function of the central nervous system, thus leading to hair loss; Excessive selenium will lead to hair loss due to autoimmune reaction and sebum overflow. (7) Diseases: Some systemic diseases, such as febrile diseases, anemia, malnutrition, liver diseases and serious chronic wasting diseases, often lead to thinning hair. (8) Gender and age: Women's hair grows faster than men's, and young people grow faster than the elderly, but this difference is not big. With the increase of age, the number of hair follicles in the head decreased significantly. According to statistics, according to the number of hair follicles per square centimeter, there are 6 15 in 20-30 years old, 485 in 30-50 years old and 435 in 80-90 years old. (9) Dyeing and perming: The chemical reaction acting on hair can cause the change of hair keratin structure and cause damage. (10) Other factors: Hair growth is slightly faster in daytime than at night, and slightly faster in summer than in winter. This is because the increase of temperature can promote metabolism, which leads to faster hair growth. X-ray can control sulfhydryl compounds in hair follicle matrix, thus causing temporary hair loss. Ultraviolet rays, drugs, trauma, chronic inflammation, skin diseases and local massage stimulation also have certain effects on hair growth and shedding.