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<.001). In 7 of the 32 patients, the preoperative serum IGF-I levels were below normal. Postoperatively these levels increased within normal range. This was also statistically significant (P=.016). Conclusion: These findings revealed that obstructive adenoid and tonsillar hypertrophy may cause decreased serum IGF-I levels by affecting the GH-IGF-I axis, and T&A is an effective therapeutic measure in these patients.