Puberty

Despite significant individual fluctuations, puberty in girls on average begins at the age of 10-13 years, in boys - 12-14, and ends in girls by 16-17 years, in boys - by 17-18. In boys, the main hormone of puberty is testosterone , which is responsible for all the processes of male formation, including bone growth in length. Despite the predominance of testosterone, a significant part of this hormone in the process of metabolism turns into estrogens , which have the ability to cover bone growth zones, but the estrogen level in boys rises much more slowly than in girls, so boys grow longer and more intensively. If before the onset of puberty, boys are on average 2 cm lower than girls, then by the end of this period boys become on average 13 cm higher than girls.

In the process of female puberty, the estrogen hormone estradiol is dominant, which causes the growth and development of mammary glands and female genital organs. Estradiol in girls begins to rise and reaches a high level earlier than in boys, so the girls reach puberty and stop growing earlier than the boys.

The onset of puberty is associated with high pulsatile production of gonadotropin releasing hormone (GnRH) in the hypothalamus , which stimulates the production of luteinizing and follicle-stimulating hormones in the pituitary gland . The reason for the increase in GnRH level is not exactly established, but it is assumed that leptin plays a large role in this, the level of which increases significantly with the onset of puberty and decreases with the end of the latter.

Genitals and fertility

The first sign of puberty in boys is an enlarged testicle (adrenarche). The testes in the period from 1 year to the onset of puberty almost do not change in size, the length is 2-3 cm and a width of 1.5-2 cm. 6 years after the onset of puberty, the testes reach a volume of 18-20 cm³, however, individual differences must be taken into account testicular sizes among men. The testes have two main functions: the production of hormones and the production of sperm , with the first starting earlier and stimulating the second. A year after the start of maturation in the morning urine of boys, sperm can be detected. The penis (penis) begins to grow shortly after the start of testicular growth. As the penis grows, erections occur and then pollutions . On average, boys reach potential fertility by the age of 13, and by 14–16 years of age.

Hair growth (adrenarche)

Pubic hair appears first, shortly after the onset of genital growth. Appearing in small quantities at the base of the penis, the hair gradually becomes thicker and occupy the entire pubic triangle, after which it spreads to the hips and along the white line of the abdomen to the navel . Then, after several months and even years, hair growth begins in the axillary regions , near the anus , above the upper lip , near the ears , around the nipples and on the chin . The sequence and speed of hair growth are subject to individual differences. Throughout life, hair continues to grow and becomes thicker on the arms, legs, chest, abdomen and back. Not all men have full facial hair growth, and not all have chest hair.

Change (breaking) of voice

Under the influence of androgens, the growth of the larynx occurs, lengthening and thickening of the vocal cords, which makes the voice lower. A change in voice usually accompanies a jump in body growth and occurs within a fairly short period of time. In this case, instability of the voice may be observed. The male voice is established by an average of 15 years, and usually precedes the growth of facial hair.

Male physique and muscles

By the end of puberty, young men have heavier bones and almost twice as much muscle mass as girls. Some bones grow much faster ( shoulders , jaws ), leading to noticeable differences in male and female physique. The increase in muscle mass begins at the end of puberty, reaching a maximum one year after a growth spurt. Muscle enlargement can continue after puberty, but more slowly.

Milk glands

Breast growth ( telarch ) is the first sign of puberty, and is observed at an average age of 10.5 years. First, under the areola, on one or both sides (the paralosal circle), a small, painful seal appears. After 6-12 months, compaction begins to be noted on both sides, it increases in size, becomes softer and goes beyond the areola. Over 2 years, the mammary glands reach a mature size and shape, the nipples become clearly pronounced. The size and shape of the mammary glands in girls have pronounced individual differences.

Pubic hair

Pubic hair appears a few months after the start of growth of the mammary glands. In 15% of girls, this symptom appears first. First, these are single hairs on the labia, spreading to the pubis in 6-12 months. Subsequently, the hair grows and covers the entire pubic triangle.

Genitals, menstruation , fertility

Under the influence of estrogen, the vaginal epithelium thickens, and the cells begin to actively exfoliate from its surface. The cervix begins to secrete a small amount of mucus. This leads to the appearance of whitish vaginal discharge - teenage whites. The ovaries and the uterus increase in size, follicles begin to grow in the ovaries. When conducting ultrasound in this period, you can see many small cysts - follicles. The first menstruation (menarche) usually occurs 2 years after the start of growth of the mammary glands, and during the first 2 years of menstruation can be irregular. In most menstrual cycles, ovulation does not occur during the first year, and during the second year occurs only in half of the cycles, therefore fertility in this period is limited, although conception is possible. In the future, the girl is considered to have reached puberty.

Body structure, fat distribution

During puberty, under the influence of a high level of estrogen, the pelvic bones grow in width, as a result of which the hips become wider. Adipose tissue grows, and by the end of puberty is twice the amount of adipose tissue of young men. Fat is deposited mainly in the area of ​​the mammary glands, hips, buttocks , shoulder girdle, pubis.

Axillary hair, body odor and acne

Under the influence of androgens in both sexes, hair growth in the axillary regions and a change in the smell of sweat due to the fatty acids that make up it are observed. Androgens also increase the secretion of fat by the sebaceous glands of the skin, which contributes to increased bacterial growth and the appearance of acne .

• Historical shift: the average age at onset of puberty has declined significantly since the 1840s, decreasing by about 4 months per decade. ^[one]
• Genetics : in 46% of girls, puberty begins at the same age as their mothers, which suggests the influence of genetic factors. The specific gene responsible for the transmission of this information by inheritance, however, remains unknown. It is believed to be the androgen hormone gene.
• Environment: hypothesis exists that cosmetics containing placenta or estrogen extracts, as well as phthalates , which are used in the manufacture of cosmetics, toys, and plastic containers, can cause earlier puberty. Wastes from pharmaceutical production of sex steroids can also be incompletely processed and determined in significant amounts in the environment. . Sex hormones are sometimes used on livestock farms and can accidentally pollute the environment. Concern is expressed ^{[by whom? ]} regarding bisphenol A , used in the manufacture of bottles for baby food, sports and medical products, as well as in the manufacture of certain food products.
• Nutrition: the nature of nutrition has the greatest influence on the onset of puberty, especially in girls. Additional calories , in addition to those required for growth and activity, are deposited in the form of subcutaneous fat, and fat is necessary for carrying and feeding offspring. Therefore, a certain amount of fat signals that the body has a sufficient supply of energy for puberty and fertility. Vegetarian families, for example, have a later onset of puberty in girls than in families that eat animal proteins.
• Society: The time of onset of puberty has racial , national, and social differences. The average age of menarche in different peoples varies from 12 to 18 years: the earliest recorded among representatives of the Negroid race, and the latest - among representatives of the Asiatic race living in high mountains.

Premature sexual development - the onset of puberty in girls under 8 years old and in boys under 9 years old ^[2] .

In pathological processes in the pineal gland and hypothalamus , changes occur in the hypothalamic-pituitary system that resemble those during normal puberty and secretion of the pituitary gonadotropin hormones, which, in turn, leads to sexual development that mimics prepubertal and puberty periods (the so-called true premature sexual development in both boys and girls, which is always isosexual). With gonadal tumors, tumors or adrenal cortical dysfunction, false premature sexual development begins: the secretion of gonadotropins does not increase, and excessive production of sex hormones by the adrenal cortex or gonadal tumors does not correspond to changes characteristic of normal prepubertal or pubertal periods, gonads remain infantile .

In girls, false premature sexual development can be heterosexual - with adrenogenital syndrome or isosexual - with ovarian tumors, in boys - isosexual.

Symptoms

Acceleration of growth and increase in body weight, advancing peers in sexual development.

In girls - an increase in mammary glands , the appearance of hair on the pubis , spotting from the vagina, an increase in the uterus , appendages, respectively, to the prepubertal or puberty periods, in some cases regular menstruation appears.

In boys - an increase in the external genitalia , the appearance of hair on the pubis and face , erection , and pollutions . Revealed vascular pattern, hyperpneumatization of the sinus of the main bone, accelerated differentiation of the skeleton. Early closure of growth zones leads ultimately to stunting.

Neurological symptoms may appear: headache , fatigue , bulimia , polydipsia , symptoms of oculomotor nerve damage .

• Gonad
• Gamete
• Ontogenesis
• Menarche
• Telarche