Molecular Genetic Studies in Isolated Growth Hormone Deficiency (IGHD)

Abstract

To screen Isolated Growth Hormone Deficiency (IGHD) patients with congenital Familial Isolated (FIGHD) and Nonfamilial Isolated Growth Hormone Deficiency (NFIGHD) for GH1gene deletions (6.7 kb,7.6 kb,7 kb) and Growth hormone releasing hormone receptor GHRHR(E72X) gene mutation and study genotype/phenotype correlation in this multicentre study. Clinical, auxologic (Ht.SDS ≤ -2.5), hormonal and MRI evaluation of hypothalamic/pituitary (HP) axis, IGF1, IGFBP3 estimation and GH stimulation test confirmed IGHD in 107 patients. Of these 107 patients, 97 consented for molecular genetic studies. Height, weight and Bone Age (BA) were obtained. PCR based restriction digestion method was used for molecular genetic analysis of patients and families. Ethics committee approval was obtained. Based on the genotype, these 97 patients (M60,F37;1.62:1) age 3 mo to 17 y belonging to 80 families (consanguinity, 15/80), were categorized into Group I with GH1 gene deletion, n = 17 (17.5 %) from 14 families, Group II with GHRHR (E72X) mutation n = 34 (35 %) from 24 families, Group III, n = 46 (47 %) from 42 families having neither of these deletions/mutations (but with sibling involvement). In Group I, homozygous 6.7 kb and 7.6 kb deletions involved 76 % and 18 %. 6.7 kb deletion with characteristic IGHD phenotype predominated in nonconsanguineous community from Rajasthan having lowest mean FBS (55.6 mg/dl, p < 0.001) and peak GH (0.03 ng/dl, p < 0.01). In Group II phenotype was IB. Twenty one of the 23 FIGHD had homozygous GHRHR(E72X) mutation and four with IGHD had heterozygous GHRHR(E72X) mutation. IGF1 and IGFBP3 were low. MRI showed hypoplastic anterior pituitary (APH) in all. Group III is not discussed in detail. Genetic background is more likely in congenital Growth Hormone Deficiency (GHD). GH1gene deletions and GHRHR(E72X) mutation with characteristic phenotypes are encountered in North Western region of India. Regional studies are essential.