Full-length IGF-1 (Mecasermin) is already approved by the FDA for the treatment of growth failure in children, and it was shown to have similar effects in male Mecp2 knockout mice, as well as in female Mecp2 heterozygous mice (Castro et al., 2014); a cautionary note is that full-length IGF-1 can worsen the metabolic syndrome of Mecp2 deficient mice (Pitcher et al., 2013). This evidence concerns the gene MECP2 and metabolic syndrome.