Establishment of reference serum insulin-like growth factor-I and insulin-like growth factor binding protein-3 levels of Tunisian children during childhood and adolescence

Background: The aim of the present study is to establish age- and sex-related reference ranges of serum IGF-I and IGF binding protein-3 (IGFBP-3) levels in a pattern of Tunisian children. Subjects and methods: Two hundred healthy Tunisian children (103 boys and 97 girls), aged between 6 and 16 yr, were considered in the study. Results: Mean serum levels of IGF-I and IGFBP-3 are observed to be higher in girls compared to boys of the same age interval. However, these differences were statistically significant only in pubertal ages (11–14 yr) for IGF-I and in pre-pubertal ages (6–10 yr) for IGFBP-3 (p<0.05). Steeper variations in IGF-I concentrations were obtained earlier in girls than in boys (11–12 vs 12–13 yr, Tanner stage 3–4). Peak of IGF-I levels are observed at almost the same age interval (12–14 yr). IGFBP-3 levels significantly increased at steeper variations of IGF-I for both sexes followed by steady values. Conclusions: Variations of IGF-I and IGFBP-3 with the considered parameters (sex, age, and puberty stage), which concord with previous studies on various populations, emphasize the importance of locally established reference levels to construct a SD score prediction model. Establishment of reference serum IGF-I and IGFBP-3 ranges during childhood and adolescence in Tunisian subjects can help to enhance the diagnostic efficiency of IGF-I and IGFBP-3 in evaluating growth disorders in our population.