Puberty

Puberty is a hormonally regulated process when sexual maturity and reproductive ability is developed, i.e., ovulation in girls and spermatogenesis in boys. The puberty is a normal function of the reproductive hypothalamus-pituitary-gonad axis.

Physiological Regulation of Puberty
The reproductive axis is already active in the fetal period (max. in the 20th week of pregnancy) and in the infancy period ("physiological minipuberty" between the 3rd and 4th month of life). After the minipuberty, activity of reproductive axis decreases (negative feedback, central inhibition) and remains low throughout the childhood until the beginning of puberty. The beginning of puberty is controlled by the neurosecretion of gonadotropin releasing hormone (GnRH) from hypothalamus. Both genetic factors and nutritional status (leptin level) influence the activation. Mature adrenal glands (adrenarche – 1–2 years before gonadarche) – the zona reticularis is activated and DHEA secretion (dehydroepiandrosterone) increases; Adrenal androgens affect the development of pubic and axillary hair, acne and body odor. The secretion of gonadotropinsincreases, the sex glands (gonadarche) mature, the production

of sex hormones (estradiol, testosterone) increases, the external and internal genitalia and secondary sex characteristics develop.
 * In short:
 * Hypotalamus: Gonadotropin-releasing hormone (GnRH) → anterior pituitary (adenohypophysis): gonadotropins (FSH, LH) → gonads (gonadarche): sex hormons (estradiol/testosteron) → development of external and internal genitalia, secondary sexual characteristics (thelarche, distribution of subcutaneous fat, etc.).
 * Anterior pituitary (adenohypophysis): ACTH → adrenal gland (adrenarche): androgens (DHEA, DHEAS) → development of pubic hair (pubarche), axillary hair development, acne, body odor.

Assessment of Sexual Development
Tanner scale (1–5):
 * development of pubic hair („P“), or axillary hair („A“);
 * breast development in female („M“);
 * genital development in male („G“) + testicular volume by using a Prader orchidometer(adult male: 17–30 ml);
 * 1 = resting stage;
 * 4 or 5 = adult stage.

Adolescence in Females

 * Thelarche (development of breast): between 8.–13. years of age (average: 10,5 years) – sign of gonadarche;
 * pubarche (beginning of pubic hair development) usually 6 months after the thelarche, but sometimes can be earlier than thelarche; sign of adrenarche;
 * the growth rate increases, peaks around 12 years of age, the volume of the ovaries and uterus increases, the proportions between the cervix and the body of uterus chage;
 * menarche: on average at 13 years of age (about a year after reaching the maximum growth rate).

Adolescence in Male

 * Gonadarche (increase of testicular volume): between 9–14 years of age (average: 11,5 years of age); beginning of puberty = testicular volume 4 ml;
 * pubic hair grows soon after the gonadarche;
 * the highest growth rate is between 13 and 14 years of age (between G3 and G4);
 * first ejaculation on average at 14 years of age;
 * dyphonia puberum (voice mutation) around the age of 14 ;
 * the beard starts to grow after the age of 15;
 * physiological epiphyseal closure (growth plate fusion) occurs soon after.

Trends in Adolescence
There is a gradual increase in body height in economically developed countries with earlier onset of puberty. The growth rate in the pre-adolescent period is increasing as well. The reason of increased growth rate is due to well fed condition of children and higher level of hygiene. Speed of reaching full sexual maturity, however, doesn't change.

Related Articles

 * Dospívání
 * Pubertas praecox • Pubertas tarda • Poruchy sexuálního vývoje
 * Vývoj močopohlavního systému • Endokrinní onemocnění gonád • Psychofyziologie lidské sexuality • Poruchy pohlavní identity