Sexual maturation generally proceeds in an established sequence in both sexes. The age at onset and rapidity of sexual development vary and are influenced by genetic and environmental factors. Sexual maturity begins earlier today than a century ago, probably because of improvements in nutrition, general health, and living conditions—eg, the average age of menarche has decreased by about 3 yr over the past 100 yr. The physiologic changes that underlie sexual maturation are discussed in discussed in Male Reproductive Endocrinology and Related Disorders and in Female Reproductive Endocrinology.

In boys, sexual changes begin with enlargement of the scrotum and testes, followed by lengthening of the penis and enlargement of the seminal vesicles and prostate. Next, pubic hair appears. Axillary and facial hair appears about 2 yr after pubic hair. The growth spurt usually begins a year after the testes start enlarging. The median age for first ejaculation (between 12½ and 14 yr in the US) is affected by psychologic, cultural, and biologic factors. First ejaculation takes place about 1 yr after penis growth accelerates. Gynecomastia, usually in the form of breast buds, is common among young adolescent boys and usually resolves within several years.

In most girls, breast budding is the first visible sign of sexual maturation, followed closely by the initiation of the growth spurt. Shortly thereafter, pubic and axillary hair appears. Menarche generally occurs about 2 yr after onset of breast development and when growth in height slows after reaching its peak. Menarche occurs within a wide range, with most girls in the US starting their periods at 12 or 13 yr. The stages of breast growth and pubic hair development can be detailed using Tanner's method (see Fig. 2: Female Reproductive Endocrinology: Puberty—when female sexual characteristics develop. and see Fig. 3: Female Reproductive Endocrinology: Diagrammatic representation of Tanner stages I to V of human breast maturation.).

If the order of sexual changes is disturbed, growth may be abnormal, and the physician should consider pathologic reasons.

Last full review/revision September 2009 by Daniel A. Doyle, MD