Serum IGF-I and IGFBP-3 levels for normal Thai children and their usefulness in clinical practice.
Serum IGF-I and IGFBP-3 levels are growth hormone (GH) dependent and reflect the endogenous GH secretion. Two hundred and forty-four healthy children were evaluated for serum IGF-I and IGFBP-3 levels and then the age-defined normal values for Thai children were constructed. The results showed that the serum IGF-I and IGFBP-3 levels were age dependent, gradually increased from birth and reached the peak values around the age of 14-16 years. In addition, we studied the IGF-I and IGFBP-3 values in 28 GH deficient children and 26 normal variant short stature (NVSS) by using our normal constructed values as the reference. To minimize the influence of age, both IGF-I and IGFBP-3 values were transformed to standard deviation score (SDS). In clinical practice, we recommend using the IGF-I SDS and IGFBP-3 SDS of -1 and -1.3 respectively as a cut-off point to discriminate between GH deficiency and NVSS to avoid risky GH provocative tests and unnecessary GH replacement with the sensitivity of 71 per cent and the specificity of 92 per cent.