High knowledge score: Why do girls have no hair under their armpits and hair under the shade?

If young women 18 years old or older, pubic hair and armpit hair still do not appear, it is called pubic hair without armpit hair. The reasons can be roughly divided into two categories: one is that the hair follicles of breast or armpit skin are insensitive or slow to testosterone, and even if there is high concentration of testosterone in the body, pubic hair and armpit hair will not grow. This kind of people often have normal breast development and their menstruation can come on time, which generally does not affect their sexual life after marriage, but they still have to give birth. The other is patients with congenital neglect or ovarian dysplasia. Besides pubic hair and armpit hair, they are often accompanied by other secondary dysplasia, such as short stature, no menstruation and naive appearance. You should go to the hospital for examination and treatment at this time.

Pubic hair is the second sexual characteristic of human beings. In the development of adolescence, women have two prominent developmental characteristics, one is the breast, and the other is the growth of pubic hair.

The growth of female pubic hair can be divided into six periods:

In the first stage, before 10 years old, there was no visible pubic hair.

In the second stage, about10-1year old, the long and soft pubic hair grows sparsely and curls slightly.

In the third stage, 12- 13 years old, pubic hair increased, gradually gathered, curled, thick and black.

In the fourth stage, 14- 15 years old, the pubic hair extends to cover the labia.

In the fifth stage, 16- 17 years old, the pubic hair extends to the genitals and becomes an adult type.

In the sixth stage, 18 years old, pubic hair is distributed to the inner thigh in a typical inverted triangle.

In a word, China girls generally begin to have pubic hair at the age of 14, and by the age of 17 and 18, the pubic hair density is basically fixed. The existence and density of pubic hair mainly depend on two factors: one is the level of androgen produced by adrenal cortex in vivo; Second, the sensitivity of pubic hair follicles to androgens. If the level of androgen produced by adrenal cortex during the development of female pubic hair is low, or the pubic hair follicle is not sensitive to androgen, pubic hair will be sparse or not grow. In reality, everyone's pubic hair density varies greatly. If women with little or no pubic hair have normal secondary sexual characteristics (such as breast development, body shape, voice change, etc. ), menstruation will come on time, indicating that there will be no problems in the development and sexual function of sexual organs, and they can live a normal sexual life and have normal reproductive ability. Pubic hair has no special effect on human body, nor is it a sign of sexual function or fertility, which has been confirmed by a large number of facts and scientific research in daily life. Therefore, women with little or no pubic hair should not worry and worry about themselves.

What really makes adolescent girls realize that their bodies are developing is the emergence of "secondary sexual characteristics". Judging from the order of secondary sexual characteristics, girls' hair germination is an early developmental signal. However, although some girls are over 18 years old, there are still no signs of hair eruption in vulva and armpit. So they are depressed and anxious, fearing that it will affect their marriage and children. Why don't girls have pubic hair and armpit hair? It turns out that human hair is divided into two categories, one is not affected by sex hormones, including hair, eyebrows and eyelashes; The other kind grows gradually under the influence of sex hormones, such as pubic hair and armpit hair. Girls' pubic hair and armpit hair grow under the stimulation of testosterone. Generally speaking, girls have pubic hair since 10- 1 1 year old. Pubic hair first appears on the skin at the pubic symphysis. Hair is thin and soft, light in color, and then gradually increases and becomes thicker and darker. Mature and finalize the design after 2-5 years.