This study will address the timing of the emergence of puberty in young boys, and will parallel the study on the emergence of puberty in young girls conducted by PROS in the early 1990s. The previous study resulted in a landmark article published in 1997 in Pediatrics (see Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice: A Study from the Pediatric Research in Office Settings Network). Recognition of the need for current population-appropriate data on the pubertal stages of children has increased since the publication of the PROS study on girls. In addition, a recent analysis of data from the National Health and Nutrition Examination Survey (NHANES) has brought into question the earlier maturity of young boys. Consequently, the medical and public health community, as well as the public, have been calling for examining trends in boys as well.

The objective of this study is to determine the current prevalence and mean ages of onset of pubertal characteristics by Tanner stage and testicular size in young boys seen pediatric practices in the United States by using standardized training materials and a curriculum prepared by the study team that trains clinicians how to effectively assess secondary sexual characteristics in boys to assure consistent results.

After standardized training, approximately 225 PROS practitioners will rate the level of sexual maturation on a cross-sectional sample of nearly 7,000 boys 6 through 16 years of age being seen for complete physical examinations. Each participating practitioner will enroll 30 consecutive boys (15 boys ages 6-12 and 15 boys ages 13-16). Estimates for mean ages of entry into a stage will be calculated by probit analysis, a technique that allows such estimates from cross-sectional data.