A cautious iodization programme bringing iodine intake to a low recommended level is associated with an increase in the prevalence of thyroid autoantibodies in the population.
Autoantibodies against the thyroid gland with thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) as the most common can often be demonstrated in serum. The effect of public iodization programmes on antibody prevalence is uncertain.
To measure the concentrations of thyroid autoantibodies in the Danish population before and after mandatory iodization of salt.
Two identical cross-sectional population studies were performed before (Cohort 1 (C1), year 1997-1998, n = 4649, median urinary iodine 61 µg/l) and 4-5 years after (Cohort 2 (C2), year 2004-2005, n = 3570, median urinary iodine 101 µg/l) mandatory iodine fortification of salt was implemented in Denmark. Blood tests were analysed for TPO-Ab and Tg-Ab using sensitive assays.
Antibodies were more frequent in C2 than in C1: TPO-Ab > 30 U/ml, C1 vs C2: 14·3 vs 23·8% (P 20 U/ml, C1 vs C2: 13·7 vs 19·9% (P