Bone age in prepubertal children with nonfamilial or familial idiopathic short stature and prepubertal short-stature children born small for gestational age: a longitudinal data analysis

Bone age (BA), an important indicator of growth and maturity, is used in diagnosis, policy decision-making, and prediction of adult height. Factors promoting bone maturation include GH, thyroid hormone, and sex hormones. Prepubertal BA is delayed compared to chronological age (CA) not only in untreated GH-deficient children but also in children with non-familial idiopathic short stature (ISS) or short stature and were born small for gestational age (SGA). Through analyzing cross-sectional data, degrees of BA delay compared with CA are approximately 1.5–2.0 yr at children aged 8–11 yr with nonfamilial ISS, and 1.0–2.0 yr until 8 yr of age in children born SGA (1). It is unclear why BA is delayed in prepubertal children without endocrine abnormalities. In contrast, BA accelerates in prepubertal obese children (2,3,4,5), and the timing of adrenarche affects bone maturation in prepubertal children with normal stature (6, 7). This study aimed to clarify the characteristics and associated factors of bone maturation in prepubertal children with nonfamilial or familial ISS and prepubertal short-stature children born SGA by analyzing longitudinal data. To my knowledge, this is the first report to evaluate BA in relation to CA using longitudinal data in short-stature children without endocrine abnormalities.