Genotypes in relation to phenotypic appearance and exposure to environmental factors in Graves' hyperthyroidism

Abstract

BackgroundGenetic polymorphisms and environmental factors are both involved in the pathogenesis of Graves' disease, but their interaction and effect on Graves' phenotypes have scarcely been investigated.ObjectiveTo test the hypothesis that subjects with susceptibility genotypes develop more severe Graves' hyperthyroidism at a younger age and after less exposure to environmental factors, with attention to gender differences.Study designA prospective observational multicenter study in 205 adult Caucasian patients with untreated first episode of Graves' hyperthyroidism.MethodsEvaluation of genotypes (HLA DRB1*03, DQA1*05, DQB1*02; CTLA4 49A/G, CT60 A/G; PTPN22 C/T) in relation to phenotypes (age, sex, severity (clinical, biochemical, and immunological)) of hyperthyroidism and environmental factors (smoking, stress questionnaires).ResultsG-alleles in CTLA4 single nucleotide polymorphisms were dose-dependently associated with younger age at the time of diagnosis and less exposure to daily hassles. In gender-specific analysis, this association is enhanced in men and attenuated in women. Males (but not females) in HLA linkage disequilibrium had more severe (biochemical and immunological) hyperthyroidism and a tendency to younger age at diagnosis, compared with those not in linkage disequilibrium.ConclusionGraves' hyperthyroidism occurs at a younger age with less exposure to environmental factors in subjects carrying susceptibility genotypes. The impact of genotypes seems to be greater in males than in females.