H19 and hereditary endocrine growth disease: DNA methylation defects involving imprinting control region 1 (ICR1) of the IGF2/H19 locus for which methylation abnormalities result in two growth disorders with opposite phenotypes: the overgrowth disorder Beckwith-Wiedemann syndrome [29] with maternal H19-ICR1 hypermethylation and the growth retardation disorder Silver–Russell syndrome [30] with paternal H19-ICR1 loss of methylation.