Autosomal-dominant isolated growth hormone deficiency (IGHD type II) with normal GH-1 gene

A novel gross indel in the growth hormone releasing hormone receptor gene of Indian IGHD patients

CONTEXT

Cohort specific mutations in the growth hormone (GH1) and growth hormone-releasing hormone receptor (GHRHR) genes have been reported worldwide in isolated growth hormone deficiency (IGHD) patients. However, limited data is available on ethnically diverse Indian IGHD patients.

OBJECTIVE

The aim of the study was to find GH1 and GHRHR gene mutations in Indian IGHD patients from two unrelated non-consanguineous families.

DESIGN

The 5' and 3' untranslated regions (UTRs) and coding regions with splice sites of the GH1 and GHRHR genes were sequenced for all patients (n=6). Family members and 20 controls were evaluated for the sequence variants identified in the index patients. Online bioinformatics tools were used to confirm mutations and their pathogenicity.

RESULTS

GHRHR gene mutations were observed in all patients. Interestingly, a novel indel g.30999250_31006943delinsAGAGATCCA was observed in both the unrelated families. Three patients were homozygous for the novel indel, two were homozygous for the previously reported p.E72X mutation and one was compound heterozygous with both the mutations (indel and p.E72X) in the GHRHR gene. The novel indel has resulted in the loss of 5' regulatory region and exon 1 of the GHRHR gene impairing the GHRHR expression. All the normal family members were heterozygous either for the indel or p.E72X mutation. None of the patients had GH1 gene mutations.

CONCLUSIONS

We describe a novel gross indel in the GHRHR gene resulting in the loss of 5' regulatory region and GHRHR exon 1 in four IGHD IB patients from two unrelated non-consanguineous Indian families.

Splice site mutations in GH1 detected in previously (Genetically) undiagnosed families with congenital isolated growth hormone deficiency type II

BACKGROUND

Congenital isolated growth hormone deficiency (IGHD) is a rare endocrine disorder that presents with severe proportionate growth failure. Dominant (type II) IGHD is usually caused by heterozygous mutations of GH1. The presentation of newly affected family members in 3 families with dominant IGHD in whom previous genetic testing had not demonstrated a GH1 mutation or had not been performed, prompted us to identify the underlying genetic cause.

METHODS

GH1 was sequenced in 3 Caucasian families with a clinical autosomal dominant IGHD.

RESULTS

All affected family members had severe growth hormone (GH) deficiency that became apparent in the first 2 years of life. GH treatment led to a marked increase in height SDS. So far, no other pituitary dysfunctions have become apparent. In the first family a novel splice site mutation in GH1 was identified (c.172-1G>C, IVS2-1G>C). In two other families a previously reported splice site mutation (c.291+1G>A, IVS3+1G>A) was found.

CONCLUSION

These data show that several years after negative genetic testing it was now possible to make a genetic diagnosis in these families with a well-defined, clearly heritable, autosomal dominant IGHD. This underscores the importance of clinical and genetic follow-up in a multidisciplinary setting. It also shows that even without a positive family history, genetic testing should be considered if the phenotype is strongly suggestive for a genetic syndrome. Identification of pathogenic mutations, like these GH1 mutations, has important clinical implications for the surveillance and genetic counseling of patients and expands our knowledge on the genotype-phenotype correlation.

Genetics of growth hormone deficiency

When a child is not following the normal, predicted growth curve, an evaluation for underlying illness and central nervous system abnormalities is required and appropriate consideration should be given to genetic defects causing growth hormone (GH) deficiency. This article focuses on the GH gene, the various gene alterations, and their possible impact on the pituitary gland. Transcription factors regulating pituitary gland development may cause multiple pituitary hormone deficiency but may present initially as GH deficiency. The role of two most important transcription factors, POU1F1 (Pit-1) and PROP 1, is discussed.

Isolated growth hormone deficiency

Isolated growth hormone deficiency (IGHD) represents conditions of GH deficiency that are not necessarily associated with other pituitary hormone deficiencies or with an organic lesion. Three sub-categories of IGHD have been clinically identified (IGHD types 1-3), and IGHD type 1 has been further separated into IGHD types 1a and b. However, this clinical sub-categorization of IGHD may need reconsideration due to the recent identification of molecular heterogeneity within each sub-type of IGHD. In a small number of children with IGHD, defects in the GH, GH-releasing hormone receptor (GHRH-R), and GH1 genes have been identified. In most cases, no cause for IGHD can be identified; however, the proportion of idiopathic IGHD cases may be decreasing due to identification of causative factors. The phenotype of IGHD is variable depending in part on the underlying genetic disorders in the affected individuals. Several studies have focused on the usefulness of MRI findings in patients with GHD but anatomic abnormalities of the pituitary gland are variable. We review current studies and the clinical, biochemical, and molecular features described for different groups of affected individuals with IGHD.