GHRHR and isolated congenital growth hormone deficiency: Recessively inherited or autosomal mutations in the gene coding for growth hormone (GH1) or in the gene coding the growth hormone releasing hormone receptor (GHRHR) are responsible for IGHD with different phenotypes: type 1A with severe growth failure (GH1, autosomal recessive), type 1B with milder growth insufficiency (GH1, GHRHR, autosomal recessive), type 2 with growth insufficiency, hypoplastic pituitary and potentially other hormone deficiencies (GH1, autosomal dominant), and type 3 (other gene mutations X-linked inherited) [2,3,4,5,6,7,8,9,10,11,12,13].