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Changes in hypothalamic-pituitary-gonadal endocrine function lead to the striking changes associated with secondary sexual development. Endocrine changes of puberty are divided into (1) gonadarche, or the awakening of gonadal action during which increased pituitary gonadotropins cause the secretion of gonadal steroids, and (2) adrenarche, or the awakening of adrenal androgen secretion caused by still undefined factors.

Stages of pubertal development are described using a sexual maturity rating scale popularized by Tanner. Staging provides an objective, consistent description of physical development (Fig. 540-1). Breast development (caused by ovarian estrogens) and pubic hair development (caused by adrenal androgens) are usually, but not always, coordinated in girls (eg, premature adrenarche or premature thelarche) so that each should be documented. Similarly, in boys, testicular/penile development and pubic hair development may not be synchronous because the adrenal gland can produce its own androgens out of sequence with testicular androgen secretion, due to either adrenal disease or adrenarche.

Figure 540-1.

A: Genital development and pubic hair growth among boys. Stage G1 (upper left), prepubertal. Stage G2 (upper right), enlargement of testis to more than 2.5 cm, appearance of scrotal reddening, and increase in rugations. Stage G3, increase in length or 4 cm volume and to a lesser extent breadth of penis with further growth of testis. Stage G4, further increase in size of penis and testes and darkening of scrotal skin. Stages G5 and G6 (lower panels), adult genitalia. Stage P1 (upper panels), preadolescent, no pubic hair. Stage P2 (middle left), sparse growth of slightly pigmented, slightly curved pubic hair mainly at the base of the penis. Stage P3 (middle right), thicker curlier hair spread laterally. Stage P4 (lower left), adult-type hair that does not yet spread to medial thighs. Stage P5 (lower right), adult-type hair spread to medial thighs. B: Appearance of pubic and labial hair among girls. Stage PH1 (upper left), prepubertal, no pubic hair. Stage PH2 (upper right, middle left), sparse growth of long, straight, or slightly curly minimally pigmented hair, mainly on labia. Stage PH3 (middle right), considerably darker and coarser hair spreading over mons pubis. Stage PH4 (lower left), thick adult-type hair that does not yet spread to the medial surface of the thighs. Stage PH5 (lower right), hair is adult type and is distributed in the classic inverse triangle. C: Breast development. Stage B1 (upper panels), prepubertal, elevation of the papilla only. Stage B2, breast buds visible or palpable with enlargement of the areola. Stage B3, further enlargement of the breast and areola with no separation of their contours (not shown). Stage B4, projection of areola and papilla to form a secondary mound over the rest of the breast. Stage B5 (lower panel), mature breast with projection of papilla ...

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