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This Article Accepted manuscript (PDF) All Versions of this Article: EJE-08-0192v1 159/3/293    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Camargo, R. Articles by Medeiros-Neto, G. PubMed PubMed Citation Articles by Camargo, R. Articles by Medeiros-Neto, G.

Thyroid and the environment: exposure to excessive nutritional iodine increases the prevalence of thyroid disorders in Sao Paulo, Brazil

R Camargo, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil
E Tomimori, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil
S Neves, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil
I Rubio, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil
A Galrao, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil
M Knobel, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil
G Medeiros-Neto, Thyroid Unit (LIM-25), Division of Endocrinology, Department of Clinical Medicine, University of Sao Paulo Medical School, Sao Paulo, Brazil

Correspondence: Ileana Rubio, Email: ilearubi{at}usp.br

Abstract

Objective: To evaluate the prevalence of chronic autoimmune thyroiditis (CAT) and iodine-induced hypothyroidism, hyperthyroidism (overt and subclinical) and goiter in a population exposed to excessive iodine intake for five years (table salt iodine concentrations: 40-100mgI/Kg salt).

Design: This was a population-based, cross-sectional study with 1,085 participants randomly selected from a metropolitan area in Sao Paulo, Brazil and conducted during the first semester of 2004.

Methods: Thyroid ultrasound examination was performed in all participants and samples of urine and blood were collected from each subject. Serum levels of TSH, free T4 and anti TPO antibodies; urinary iodine concentration, thyroid volume and thyroid echogenicity were evaluated. We also analyzed table salt iodine concentrations. Results: At the time the study was conducted table salt iodine concentrations were within the new official limits (20-60mgI/Kg salt). Nevertheless, in 45.6% of the participants, urinary iodine excretion was excessive (above 300 µg/L) and in 14.1% it was higher than 400 µg/L. The prevalence of chronic autoimmune thyroiditis (including atrophic thyroiditis) was 16.9% (183/1,085), women were more affected than men (21.5% vs. 9.1% respectively, p=0.02). Hypothyroidism was detected in 8.02% (87/1,085) of the population with CAT., Hyperthyroidism was diagnosed in 3.3% of the individuals (36/1,085) and goiter was identified in 3.1% (34/1,085).

Conclusions: Five years of excessive iodine intake by the Brazilian population may have increased the prevalence of chronic autoimmune thyroiditis and hypothyroidism in subjects genetically predisposed to thyroid autoimmune diseases. Appropriate screening for early detection of thyroid dysfunction may be considered during excessive nutritional iodine intake.