Previous studies showed that low IGF-1 levels correlate, in CHH patients, with reduced erythropoiesis [34], but true GH deficiency, defined as insufficient response to GHRH (growth hormone-releasing hormone) stimulation, was never demonstrated [35]; moreover, GH treatment has proven to be of little value in CHH patients [36], as well as in other skeletal dysplasias [37,38]. This evidence concerns the gene IGF1 and cartilage-hair hypoplasia.