A Population-Based Study of Chronic Autoimmune Hypothyroidism in Danish Twins

Publisher Website
Google Scholar
Abstract
Hashimoto's thyroiditis (HT), atrophic thyroiditis (AT), and Graves' disease are autoimmune thyroid diseases in which genetic factors are suspected to play an important role in disease suscepti- bility. In a recent population-based twin study we rendered it prob- able that a substantial part of the susceptibility to Graves' disease is attributable to genetic factors. At present there are no population- based twin studies supporting such a genetic influence in the etiology of HT/AT. To elucidate whether there is a genetic influence in the etiology of HT/AT, we studied the distribution of HT/AT in a population-based sample of 2945 Danish female-female twin pairs (5890 individuals) born between 1953 and 1972. Information on hypothyroidism was obtained from a nationwide questionnaire survey in 1994. Informa- tion from hospitals, out-patient clinics, general practitioners, and specialists was sought to verify the diagnosis. The overall prevalence of autoimmune hypothyroidism was 0.41% (24 of 5890). The prevalence did not differ between monozygotic and dizygotic twins (0.42% and 0.40%, respectively). The crude proband- wise concordance rates were significantly higher for monozygotic com- pared to dizygotic twin pairs: 0.55 (95% confidence interval, 0.23- 0.83) vs. 0.0 (95% confidence interval, 0.0 - 0.25; P 5 0.01). All of the healthy cotwins (n 5 15) of twins with clinically overt autoimmune hypothyroidism were biochemically euthyroid. Overall, regardless of zygosity 53% (8 of 15) of the healthy cotwins were positive for anti- thyroid antibodies. The prevalence of autoantibodies among the monozygotic cotwins was 80% (4 of 5) and 40% (4 of 10) among dizy- gotic cotwins (P 5 0.36). In conclusion, the higher concordance rate in monozygotic com- pared to dizygotic pairs indicates that genetic factors play a role in the etiology of HT/AT among Caucasian women living in areas with bor- derline iodine deficiency. However, the fact that the concordance rate among MZ twins was below 1 suggests that environmental factors also are of etiological importance. (J Clin Endocrinol Metab 85: 536 - 539, 2000)

This publication has 0 references indexed in Scilit: