Clinical Relevance of Environmental Factors in the Pathogenesis of Autoimmune Thyroid Disease
2016; Academya Publishing Co.; Volume: 31; Issue: 2 Linguagem: Inglês
10.3803/enm.2016.31.2.213
ISSN2093-5978
Autores Tópico(s)Adrenal Hormones and Disorders
ResumoContext: Iodine fortification (IF) of salt was introduced in Denmark in 1998.Little is known about the effect of a minor increase in iodine intake on the incidence of hypothyroidism.We prospectively identified all new cases of overt hypothyroidism in two areas of Denmark before and for the first 7 yr after IF had been introduced. Methods:A computer-based register was used to identify continuously all new cases of overt hypothyroidism in two subcohorts with previous moderate and mild iodine deficiency (ID), respectively (Aalborg, n ϭ 310,124, urinary iodine ϭ 45 g/liter; and Copenhagen, n ϭ 225,707, urinary iodine ϭ 61 g/liter).Data were obtained 1) before IF (1997)(1998), 2) during voluntary IF (1999IF ( -2000)), 3) during early (2001)(2002) and 4) during late (2003)(2004)(2005) period with mandatory IF. Results:The overall incidence rate of hypothyroidism increased during the study period: baseline, 38.3/100,000⅐yr; voluntary IF, 43.7 (not significant vs. baseline); early mandatory IF, 48.7 [vs.baseline, rate ratio (RR) ϭ 1.27; 95% confidence interval (CI) ϭ 1.10 -1.47]; and late mandatory IF, 47.2 (vs.baseline, RR ϭ 1.23; 95% CI ϭ 1.07-1.42).There was a geographic difference because hypothyroidism increased only in the area with previous moderate ID: Aalborg, late mandatory IF vs. baseline, 40.3/29.7 (RR ϭ 1.11; 95% CI ϭ 1.11-1.66);Copenhagen, 56.7/51.6 (RR ϭ 1.10; 95% CI ϭ 0.90 -1.34).The increase occurred in young and middle-aged adults. Conclusion:Even a cautious iodization of salt was accompanied by a moderate increase in the incidence rate of overt hypothyroidism.This occurred primarily in young and middle-aged subjects with previous moderate ID. (
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