We describe severe thyrotoxicosis in young members of a family with nonautoimmune hyperthyroidism caused by a C672W germline mutation in exon 10 of TSHR gene. In this family, lack of genotype-phenotype correlation and anticipation across generations could be linked to an increased iodine intake as recently observed in France.
Keywords: Familial nonautoimmune hyperthyroidism; iodine intake; mitral valve prolapse; proptosis; stimulating TSH receptor gene mutation.