Puberty Timing Remains Unchanged

Abstract

It has been presumed by the media and the public that puberty is occurring earlier now than in past decades. This is the result of reports of earlier breast development in girls (Tanner stage 2, Br2) and earlier genital development (Tanner genital stage 2, G2) in boys. Nonetheless, owing to the lack of representative data, the intra- and inter-observer variability in Tanner staging, and the fact that initial sex hormone-driven physical changes do not always indicate the onset of puberty, bona fide evidence of an earlier pubertal onset is not available. The gold standard verifying pubertal onset involves documentation of hormonal responsiveness of the hypothalamic–pituitary–gonadal (HPG) axis. The evidence cited for an earlier onset of puberty involves the age of the first physical changes of puberty. In girls, the appearance of breast may simply be due to fatty tissue deposition, particularly in overweight children; alternatively, breast tissue may be a consequence of non-HPG-stimulated estrogen production. In males, genital staging is poorly defined and therefore subjective and prone to significance within and between observer disagreements. Inexperienced observers, unacquainted with the normal variation in prepubertal genital size and appearance, may erroneously assign G2 based on size alone. This is a possible explanation of recent studies showing a high percentage of 9-year-old boys in G2 in recent surveys in contrast to findings in the last 1970s. Data remain insufficient because of problems with sample size and selection, race, socioeconomic status (SES), assessment, and statistical methods to conclude that there is a significant continuation of the secular trend toward an earlier pubertal onset in boys or girls.