GHRHR and isolated congenital growth hormone deficiency: For over 25 years, we have been studying subjects with isolated congenital growth hormone (GH) deficiency (IGHD) residing in Itabaianinha in northeastern Brazil and discovered that their IGHD is due to an autosomal recessive null mutation (c.57+1G>A) in the GH-releasing hormone receptor (GHRHR) gene ( 3 – 5 ).