GH1 C.291 + 34G>C in a Growth Hormone Deficient Pedigree

Abstract

Background: Heterozygous loss of function mutations in GH1 are a cause of autosomal dominant isolated growth hormone deficiency (GHD) or IGHD type II. However, this condition is rare and a genotype/phenotype association is often based on single case or pedigree reports. Clinical Case: The male proband was born at 38 weeks following an uncomplicated pregnancy, birthweight 2585 gm (˗1.3SD), length 43 cm (˗2.7SD). At 20 months old: length ˗3.2SD, weight/length 16%. Peak growth hormone (GH) levels 4.42 ng/mL and 3.2 ng/mL following clonidine and arginine stimulation, respectively; cortrosyn-stimulated cortisol was 41.4 mcg/dL. Prolactin was 61.2 ng/mL (reference range 2.6 to 13.1 ng/mL); T4 and TSH levels were normal. Magnetic resonance imaging showed a flattened anterior pituitary gland, consistent with empty sella, with normal bright spot. He has had an intermittent and variable response to GH treatment due to noncompliance; recent recorded height was ˗3.6SD at 13.9 and he was early pubertal. Father had a history of childhood growth hormone treatment and is 151 cm tall, 2 paternal aunts did not receive treatment and are 145 cm tall, 3 children of these aunts are diagnosed with GHD. There is no maternal family history of GHD; mother is 155 cm. Proband testing revealed heterozygous GH1 c.291 + 34G>C (EGL Genetics), classified as a variant of unknown significance; father was also found to have this variant, mother was negative. Genetic testing for of additional family members is under consideration. Conclusion: Nine of 96 heterozygous GH1 variants are located in intron 3. Two have been classified as pathogenic and are predicted to cause exon skipping. Our proband’s variant cannot be considered a canonical splice site or in a mutational hot spot but has extremely low frequency in population databases. Functional studies clan clarify if our proband’s variant results in a 17.5 kDa GH isoform and dominant negative effect on full length GH production with potential detrimental effects on other anterior pituitary hormones. We present the second GHD pedigree with GH1 c.291 + 34G>C mutation. As in the previous report (1), no other hormone deficiencies are identified, despite the appearance of an empty sella for our proband. Reference: (1) Cho SY, Ki, CS, Park, HD, et al. Genetic investigation of patients with undetectable peaks of growth hormone after two provocation tests. Clin Endocrinol 2013; 78: 317-20.