Examples for this include patients with short stature with IGF-1 gene mutations that produce bioinactive IGF-1 who display elevated immunoreactive IGF-1 levels [37], short patients with mutant GH gene and high levels of measured growth hormone which is bioinactive [25], as well as patients with glucocorticoid deficiency caused by a mutation leading to bioinactive ACTH and elevated immunoreactive ACTH levels [26]. The gene discussed is IGF1; the disease is familial glucocorticoid deficiency.