IGF1 and Global developmental delay: Homozygous mutations of the IGF1 gene, causing its complete loss of function, result in extreme prenatal and postnatal growth impairment and are frequently associated with various forms of microcephaly, developmental delay and sensorineural deafness due to the IGF-1 role in nervous system development in utero.30 Heterozygous mutations of the IGF1 gene can cause mild growth failure characterized by lower birth weight, height and head circumference but normal hearing.31 Although height SD score (SDS) was significantly lower than in the non-carriers, it was still within the normal range.31