Background: The objective of this survey was to examine the prevalence of thyroid disease including autoimmunity in Norway.
Materials and methods: All 94,009 inhabitants aged 20 and above in Nord-Trøndelag county, Norway were invited to participate in a health survey.
Results: The prevalence of formerly diagnosed hyperthyroidism was 2.5% in women and 0.6% in men, hypothyroidism 4.8% and 0.9% respectively, increasing with age. In individuals without a history of thyroid disease the median, 2.5 and 97.5 percentiles for TSH (mU/l) were 1.8 and 0.49-5.7 for women and 1.5 and 0.56-4.6 for men. When excluding individuals with positive thyroid peroxidase antibodies (TPOAb), the 97.5 percentiles were 3.6 mU/l for women and 3.4 mU/l for men. The prevalence of pathological TSH values in women and men were TSH > or = 10 mu/l 0.9% and 0.4%; TSH 4.1-9.9 mU/l 5.1% and 3.7%; TSH < or = 0.05 mU/l 0.5% and 0.2%. The prevalence of positive TPOAb was 13.9% in women and 2.8% in men, the lowest percentage was seen with TSH 0.2-2.0 mU/l and increased both with higher and lower TSH values and was higher in women except for those with TSH > or = 10 mU/l (85% TPOAb positive).
Conclusion: In spite of a high prevalence of recognised thyroid disease in the population a considerable number have undiagnosed thyroid dysfunction and positive TPOAb.