Thyrotoxicosis after iodine fortification. A 21‐year Danish population‐based study

Petersen, Mads; Knudsen, Nils; Carlé, Allan; Andersen, Stig; Jørgensen, Torben; Perrild, Hans; Ovesen, Lars; Rasmussen, Lone Banke; Thuesen, Betina Heinsbæk; Pedersen, Inge Bülow

doi:10.1111/cen.13751

Cited by 34 publications

(45 citation statements)

References 29 publications

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“…In Switzerland, in 1980, the yearly incidence of toxic nodular goiter and GD together rose by 27% following the correction of iodine deficiency, but from 1980 to 1996, the incidence of both thyroid disorders decreased to levels lower than the baseline annual incidence of about 35 cases per 100,000: toxic nodular goiter decreased to 6.9 per 100,000, and GD to 20.6 per 100,000 . A similar pattern of iodine‐induced hyperthyroidism, a transient rise followed by a decrease to incidence levels lower than before the increase in iodine intake has been reported in Sweden and Denmark . Overt and subclinical hyperthyroidism are described in Table .…”

Section: Thyroid Disorders Associated With Iodine Excessmentioning

confidence: 96%

“…Incidence of iodine‐induced hyperthyroidism with implementation of iodine fortification or supplementation has been reported . The incidence increase is generally considered transient: exposed populations show a 5‐to‐7‐year increase in incidence of iodine‐induced hyperthyroidism; however, with time, both the prevalence of iodine‐induced hyperthyroidism and nodular goiters decreases to levels below those observed before iodine overexposure.…”

Section: Thyroid Disorders Associated With Iodine Excessmentioning

confidence: 99%

“…The definition of iodine "excess" in these individuals, therefore, depends upon previous iodine status. Older persons with nodular goiter having had a longer exposure to iodine deficiency are at highest risk, 10,14,138 and living in an iodine-deficient area has been proposed as a risk factor per se. 141,168 The degree of effect depends upon the longevity and severity of iodine deficiency, and the degree of increased exposure to iodine.…”

Section: Iodine-induced Hyperthyroidismmentioning

confidence: 99%

“…Adverse consequences of excess iodine intakes have been reported, but thyroid dysfunction may also occur at lower intake levels . Transient increases in the incidences of hypothyroidism or thyroid autoimmunity in previously iodine‐deficient areas may occur even during careful implementation of USI, and iodine‐induced hyperthyroidism has been observed at daily iodine intakes of less than 300 μg …”

Section: Introductionmentioning

confidence: 99%

“…8 Adverse consequences of excess iodine intakes have been reported, 9 but thyroid dysfunction may also occur at lower intake levels. 7 Transient increases in the incidences of hypothyroidism or thyroid autoimmunity in previously iodine-deficient areas may occur even during careful implementation of USI, 6,10-12 and iodine-induced hyperthyroidism has been observed at daily iodine intakes of less than 300 g. 13,14 The aim of our paper is to review the association between excess iodine intake and thyroid function, including the etiology, physiological responses, and consequences of excess iodine intakes. In addition, we provide guidance on the relevant biomarkers that are used to assess excess iodine intake in population monitoring, with an emphasis on the UIC and Tg.…”

Section: Introductionmentioning

confidence: 99%

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Excess iodine intake: sources, assessment, and effects on thyroid function

Farebrother

Zimmermann

Andersson

2019

Annals of the New York Academy of Sciences

204

131

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Iodine is essential for thyroid hormone synthesis. High iodine intakes are well tolerated by most healthy individuals, but in some people, excess iodine intakes may precipitate hyperthyroidism, hypothyroidism, goiter, and/or thyroid autoimmunity. Individuals with preexisting thyroid disease or those previously exposed to iodine deficiency may be more susceptible to thyroid disorders due to an increase in iodine intake, in some cases at intakes only slightly above physiological needs. Thyroid dysfunction due to excess iodine intake is usually mild and transient, but iodine‐induced hyperthyroidism can be life‐threatening in some individuals. At the population level, excess iodine intakes may arise from consumption of overiodized salt, drinking water, animal milk rich in iodine, certain seaweeds, iodine‐containing dietary supplements, and from a combination of these sources. The median urinary iodine concentration (UIC) of a population reflects the total iodine intake from all sources and can accurately identify populations with excessive iodine intakes. Our review describes the association between excess iodine intake and thyroid function. We outline potential sources of excess iodine intake and the physiological responses and consequences of excess iodine intakes. We provide guidance on choice of biomarkers to assess iodine intake, with an emphasis on the UIC and thyroglobulin.

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Section: Thyroid Disorders Associated With Iodine Excessmentioning

confidence: 96%

Section: Thyroid Disorders Associated With Iodine Excessmentioning

confidence: 99%

Section: Iodine-induced Hyperthyroidismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Excess iodine intake: sources, assessment, and effects on thyroid function

Farebrother

Zimmermann

Andersson

2019

Annals of the New York Academy of Sciences

204

131

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Effectiveness of increased salt iodine concentration on iodine status: trend analysis of cross-sectional national studies in Switzerland

et al. 2019

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Iodoprophylaxis and thyroid autoimmunity: an update

Teti¹,

Panciroli

Nazzari

et al. 2021

Immunol Res

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Adequate iodine intake is necessary for normal thyroid function. Iodine deficiency is associated with serious complications, but also iodine excess can lead to thyroid dysfunction, and iodine supplementation aimed to prevent iodine deficiency disorders has been associated with development of thyroid autoimmunity. The epidemiology of thyroid diseases has undergone profound changes since the implementation of iodoprophylaxis, notably by means of iodine-enriched salt, specifically resulting in decreased prevalence of goiter and neonatal hypothyroidism, improved cognitive function development in infancy, and reduced incidence of more aggressive forms of thyroid cancer. The main question we address with this review is the clinical relevance of the possible effect on autoimmunity exerted by the use of iodine-enriched salt to correct iodine deficiency. In animal models, exogenous iodine is able to trigger or exacerbate thyroid autoimmunity, but it is still not clear whether the observed immunological changes are due to a direct effect of iodine on immune response, or whether they represent a secondary response to a toxic effect of iodine on thyroid tissue. Previous iodine status of a population seems to influence the functional thyroid response to increased iodine intake and possibly the development of thyroid autoimmunity. Moreover, the prevalence of thyroid antibodies, regarded as hallmark of autoimmune thyroid disease, varies between populations under the influence of genetic and environmental factors, and the presence of thyroid antibodies does not always coincide with the presence of thyroid disease or its future development. In addition, the incidence of autoimmune diseases shows a general increasing trend in the last decades. For all these reasons, available data are quite heterogeneous and difficult to analyze and compare. In conclusion, available data from long-term population surveys show that a higher than adequate population iodine intake due to a poorly controlled program of iodine prophylaxis could induce thyroid dysfunction, including thyroid autoimmunity mostly represented by euthyroid or subclinical hypothyroid autoimmune thyroiditis. Close monitoring iodine prophylaxis is therefore advised to ensure that effects of both iodine deficiency and iodine excess are avoided.

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Thyrotoxicosis after iodine fortification. A 21‐year Danish population‐based study

Abstract: The rise in thyrotoxicosis incidence with cautious mandatory IF returned to baseline level after 7-8 years and levelled out at 33% below baseline in the population with previously moderate ID after 16-17 years.

Cited by 34 publications

References 29 publications

Excess iodine intake: sources, assessment, and effects on thyroid function

Excess iodine intake: sources, assessment, and effects on thyroid function

Effectiveness of increased salt iodine concentration on iodine status: trend analysis of cross-sectional national studies in Switzerland

Iodoprophylaxis and thyroid autoimmunity: an update

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