Precocious, delayed, or atypical patterns of pubertal development may be a sign of underlying pathology or disease.

Puberty is a normal developmental process that results in reproductive capability and sexual maturity. Initiation of puberty and normal progression through its stages requires an intact hypothalamic-pituitary-gonadal (HPG) axis. The onset of puberty follows the return of pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. GnRH stimulates the release of leuteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland, which in turn stimulate the gonads to mature. This process is termed gonadarche, and results in the production of sex steroids, predominantly testosterone and estradiol. Concurrently, the zona reticularis of the adrenal gland matures, resulting in the production of adrenal androgens. These hormones produce the secondary sex characteristics, such as pubic hair, axillary hair, body odor, and acne. The exact triggers for adrenarche are not known.

Traditionally, the expert consensus regarding the normal timing of puberty and the stages of pubertal development have been based on studies done by Marshall and Tanner more than 40 years ago in Britain. These studies documented that most girls experienced breast development and menarche between the ages of 8.5 to 13 years, and most boys showed signs of genital development between the ages of 9.5 to 13.5 years. In girls, thelarche, or breast development, is usually the first sign of puberty and occurs at an average age of approximately 11 years. Menarche typically occurs 2.5 years after thelarche, at an average age 13.5 years. In boys, increased testicular volume is typically the first sign of puberty and occurs at an average age of nearly 12 years. Enlargement of the penis occurs 6 to 18 months later. Of note, the timing of the growth spurt associated with puberty occurs later for boys than for girls. In general, the variable timing of the onset and progression of puberty is primarily related to genetic factors, but several environmental factors also play a role. The five stages of puberty are reviewed in Table 129.1.