Objective: Obstructive adenoid and tonsillar hyperplasia may present with retardation of growth. Interruption of growth hormone-insulin-like growth factor I axis resulting from abnormal nocturnal growth hormone secretion is among the postulated causes. Growth hormone (GH) mediates its anabolic effects on tissues through insulin-like growth factor I (IGF-I). Most of the circulating IGF-I is bound to insulin-like growth factor binding protein 3 (IGFBP3). The objective of this study is to determine blood serum levels of IGF-I and IGFBP3 in patients with adenoid and tonsillar hypertrophy. Furthermore, we want to investigate the effect of tonsillectomy and adenoidectomy (T&A) on these levels.Study Design: The blood serum levels of IGF-I and its binding protein IGFBP3 were examined in 41 randomly selected children with a diagnosis of upper airway obstruction resulting from hypertrophic tonsils and adenoids.Methods: Blood samples were taken preoperatively and repeated at 3 to 6 months (mean, 4.3 mo) following T&A operation. Coated-tube immunoradiometric assay (IRMA) method was used to analyze IGF-I and IGFBP3 levels.Results: Thirty-two of 41 children were eligible for the analysis. When the preoperative and postoperative results were compared, it was found that there was a statistically significant increase in serum IGF-I and IGFBP3 levels in these 32 children (P