A Family with Congenital Hypothyroidism Caused by a Combination of Loss-of-Function Mutations in the Thyrotropin Receptor and Adenylate Cyclase-Stimulating G Alpha-Protein Subunit Genes

Background: Resistance to thyrotropin (TSH) causes congenital hypothyroidism (CH). TSH receptor (TSHR) and adenylate cyclase-stimulating G alpha protein subunit (GNAS) loss-of-function mutations cause TSH resistance. We describe a family with TSH resistance and CH bearing a combination of inactivating mutations in TSHR and GNAS genes. We describe studies to determine the molecular mechanisms involved in TSH resistance in this family. Methods: DNA sequencing to identify TSHR and GNAS gene mutations was performed. In vitro effects of the mutations on cAMP production and TSH binding were investigated in COS7 cells. cAMP production was evaluated by transfecting a cAMP response element (CRE)-luciferase reporter with pSVL-TSHR and pSVK3-GNAS vectors. For binding studies, cells transfected with pSVL-TSHR vectors were incubated with iodine-125 bovine TSH (125IbTSH). Results: Family members with and without CH were heterozygous for the TSHR mutant p.E34K or the GNAS mutant c.750_751insA (=GNASMut). The propositus ...