CONTEXT: Few data are available on the effect of iodine fortification on thyroid function development in a population. OBJECTIVE: Our objective was to evaluate changes in thyroid function after iodine fortification in a population and to identify predictors for changes in serum TSH. DESIGN AND SETTING: A longitudinal population-based study of the DanThyr C1 cohort examined at baseline (1997-1998) and reexamined 11 yr later (2008-2010). The mandatory program for iodization of salt was initiated in 2000. PARTICIPANTS: A total of 2203 individuals, with no previous thyroid disease, living in two areas with different levels of iodine intake, with measurement of TSH and participation in follow-up examination were included in the analysis. MAIN OUTCOME MEASURE: Change in serum TSH was evaluated. RESULTS: During the 11-yr follow-up, mean TSH increased significantly from 1.27 mU/liter [95% confidence interval (CI) = 1.23-1.30] to 1.38 mU/liter (CI = 1.34-1.43) (P < 0.001). The most pronounced increase was observed in the area with the highest iodine intake [1.30 mU/liter (CI = 1.25-1.35) to 1.49 mU/liter (CI = 1.43-1.55), P < 0.001], whereas the increase was not significant in the low-iodine-intake area [1.24 (CI = 1.19-1.29) to 1.28 (CI = 1.23-1.34), P = 0.06)]. Change in TSH was positively associated with the presence of thyroid peroxidase antibody at baseline (P < 0.001) and negatively associated with baseline thyroid enlargement (P < 0.001) and multiple nodules (P < 0.001). CONCLUSIONS: Even small differences in the level of iodine intake between otherwise comparable populations are associated with considerable differences in TSH change at the 11-yr follow-up. Multinodular goiter predicted a less pronounced TSH increase during follow-up, which may be explained by iodine-dependent activity of autonomous nodules.
CONTEXT: Few data are available on the effect of iodine fortification on thyroid function development in a population. OBJECTIVE: Our objective was to evaluate changes in thyroid function after iodine fortification in a population and to identify predictors for changes in serum TSH. DESIGN AND SETTING: A longitudinal population-based study of the DanThyr C1 cohort examined at baseline (1997-1998) and reexamined 11 yr later (2008-2010). The mandatory program for iodization of salt was initiated in 2000. PARTICIPANTS: A total of 2203 individuals, with no previous thyroid disease, living in two areas with different levels of iodine intake, with measurement of TSH and participation in follow-up examination were included in the analysis. MAIN OUTCOME MEASURE: Change in serum TSH was evaluated. RESULTS: During the 11-yr follow-up, mean TSH increased significantly from 1.27 mU/liter [95% confidence interval (CI) = 1.23-1.30] to 1.38 mU/liter (CI = 1.34-1.43) (P < 0.001). The most pronounced increase was observed in the area with the highest iodine intake [1.30 mU/liter (CI = 1.25-1.35) to 1.49 mU/liter (CI = 1.43-1.55), P < 0.001], whereas the increase was not significant in the low-iodine-intake area [1.24 (CI = 1.19-1.29) to 1.28 (CI = 1.23-1.34), P = 0.06)]. Change in TSH was positively associated with the presence of thyroid peroxidase antibody at baseline (P < 0.001) and negatively associated with baseline thyroid enlargement (P < 0.001) and multiple nodules (P < 0.001). CONCLUSIONS: Even small differences in the level of iodine intake between otherwise comparable populations are associated with considerable differences in TSH change at the 11-yr follow-up. Multinodular goiter predicted a less pronounced TSH increase during follow-up, which may be explained by iodine-dependent activity of autonomous nodules.
Authors: Annewieke W van den Beld; Jean-Marc Kaufman; M Carola Zillikens; Steven W J Lamberts; Josephine M Egan; Aart J van der Lely Journal: Lancet Diabetes Endocrinol Date: 2018-07-17 Impact factor: 32.069
Authors: Simone A Johner; Michael Thamm; Peter Stehle; Ute Nöthlings; Eugen Kriener; Henry Völzke; Roland Gärtner; Thomas Remer Journal: Thyroid Date: 2014-06-05 Impact factor: 6.568
Authors: Layal Chaker; Christine Baumgartner; M Arfan Ikram; Abbas Dehghan; Marco Medici; W Edward Visser; Albert Hofman; Nicolas Rodondi; Robin P Peeters; Oscar H Franco Journal: Eur J Epidemiol Date: 2014-09-02 Impact factor: 8.082