IGF-1 600 ELISA Insulin-like growth factor I (IGF-1) is a polypeptide of 70 amino acids (7650 daltons). The molecule shows approximately 50% sequence homology with Proinsulin and has a number of biological activities similar to insulin. The level of IGF-1 correlates with age. The measurement of serum IGF-1 is of recognized value in children with growth disorders and in the diagnosis and monitoring of acromegaly.