Puberty and precocious puberty
Puberty
- Puberty refers to the series of events leading to sexual maturity. It is a time of accelerated growth, skeletal maturation, development of secondary sexual characteristics, and achievement of fertility. The age at which puberty occurs has dropped significantly over the past 150 years due to improved nutrition and living conditions.
- Adolescence is the period of psychological and social transition between childhood and adulthood. Adolescence largely overlaps the period of puberty, but its boundaries are less precisely defined and it refers as much to the psychosocial and cultural characteristics of development during the teen years as to the physical changes of puberty.
- Thelarche (breast development) is the first sign of puberty. It usually begins between 8 and 13 years of age and is associated with increased estrogen production.
- Adrenarche (development of pubic and axillary hair) is the second stage in maturation and typically occurs between 11 and 12 years of age. Axillary hair usually appears after the growth of pubic hair is complete.
- Menarche (onset of menstruation) usually occurs 2–3 years after thelarche at an average age of 11–13 years. Initial cycles are often anovulatory and irregular.
- The major determinant of the timing of puberty is genetic. Puberty begins earliest in black girls, followed by Hispanic and white girls. Environmental factors (general health, nutritional status, geographic location) are also important.
Biologic basis of puberty
- Pubertal changes are triggered by the maturation of the hypothalamic–pituitary–ovarian axis.
- The onset of puberty is heralded by hypothalamic pulsatile release of gonadotropin-releasing hormone (GnRH).
- Increased pituitary gonadotropin (luteinizing hormone [LH], follicle-stimulating hormone [FSH]) production in response to pulsatile GnRH is the endocrinologic hallmark of puberty.
- The final maturation phase is the development of a cyclic midcycle surge of LH in response to the positive feedback of the steroid hormones, primarily estradiol-17β. This midcycle LH surge induces ovulation and the normal female menstrual cycle (see Chapter 2).
