The use of GnRH stimulation in delayed puberty relies on the premise that the gonadotrophin response to GnRH or GnRHa will be greater in CDGP than in CHH, as individuals with CDGP have previously been exposed to endogenous GnRH whilst individuals with CHH have not been exposed to endogenous GnRH or lack functional GnRH receptors [20]. This evidence concerns the gene GNRH1 and cartilage-hair hypoplasia.