Determination of insulin-like growth factor I in children: Normal values and clinical use

valid diagnostic information regarding children exhibiting short stature. T hus, an IGF-I value should always be evaluated together with auxological in formation and GH testing results before a decision is taken on whether or n ot to start GH therapy. Circulating insulin-like growth factor I (IGF-I) le vels are stable throughout the day and correlate, with pulsatile endogenous growth hormone (GH) secretion. A single measurement of IGF-I may, therefor e, provide information on the GH secretory status of an individual. The cli nical use of IGF-I determination in the evaluation of short stature in chil dren suspected of GH deficiency will be discussed. Previous methodological problems have now mostly been overcome, and IGF-I can be determined in seru m from healthy children, although concentrations exhibit large inter-indivi dual variations relating to age, gender and pubertal maturation. These vari ations must be taken into account before IGF-I can be evaluated in a clinic al situation, and before it can be stated whether a certain value is too lo w for a given age. The diagnostic sensitivities of IGF-I reported in relati on to the outcome of GH provocative testing are variable (47-100%). This va riability probably results from the use of different IGF-I assays, IGF-I re ference ranges, and different GH testing procedures. When proper IGF-I assa ys and reference ranges are used, however, IGF-I determination results in C opyright (C) 2001 S. Karger AG, Basel.