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

Pedersen, Inge Bülow; Knudsen, Nils; Carlé, Allan; Vejbjerg, Pernille; Jørgensen, Torben; Perrild, Hans; Ovesen, Lars; Rasmussen, Lone Banke; Laurberg, Peter

doi:10.1111/j.1365-2265.2011.04008.x

Cited by 141 publications

(121 citation statements)

References 34 publications

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“…It is well documented that the introduction of iodine into areas with a history of iodine deficiency results in a temporary increase in the incidence of thyrotoxicosis (Bürgi, 2010;Pedersen et al, 2011), which gradually resolves after 2-5 years (Zimmermann, 2008). Regular and ongoing monitoring is required to ensure that population iodine intakes achieve recommended ranges without excessive intakes in some sectors of the population (Australian Institute of Health and Welfare, 2011).…”

Section: Discussionmentioning

confidence: 99%

Improvement in iodine status of pregnant Australian women 3years after introduction of a mandatory iodine fortification programme

Charlton

Yeatman

Brock

et al. 2013

Preventive Medicine

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Section: Discussionmentioning

confidence: 99%

Improvement in iodine status of pregnant Australian women 3years after introduction of a mandatory iodine fortification programme

Charlton

Yeatman

Brock

et al. 2013

Preventive Medicine

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“…Surveys from Denmark (58), Greece (61), Sri Lanka (62), China (63) and parts of Africa (64) have all documented increases in the occurrence of thyroid dysfunction or autoimmunity in the wake of iodisation. In addition, the prevalence of both TPO-Ab and Tg-Ab (albeit low titre) was higher 4-5 years after cautious iodine fortification of salt was introduced in Denmark, particularly in young women (65). These populationlevel increases in the adult incidence of autoimmune thyroiditis thus seem an inevitable by-product of iodisation but should not deter future efforts at iodisation as the potential adverse effects of iodine deficiency on child development far outweighs the risk of correctable hypothyroidism in adults.…”

Section: Clinical Significance Of the Findingsmentioning

confidence: 99%

THERAPY OF ENDOCRINE DISEASE: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis

Taylor

Okosieme

Dayan

et al. 2014

European Journal of Endocrinology

136

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Background: Although the detrimental effects of severe iodine deficiency are well recognised, the benefits of correcting mild-to-moderate iodine deficiency are uncertain. Objectives: We undertook a systematic review of the impact of iodine supplementation in populations with mildto-moderate iodine deficiency. Methods: We searched Medline and the Cochrane library for relevant articles published between January 1966 and April 2013, which investigated the effect of iodine supplementation on maternal and newborn thyroid function, infant neurodevelopment and cognitive performance in school-age children. The quality of studies was graded and eligible trials were evaluated in the meta-analysis. Results: Nine randomised controlled trials (RCTs) and eight observational studies met the inclusion criteria. Controlled trials on infant neurodevelopment were lacking; gestational iodine supplementation reduced maternal thyroid volume and serum thyroglobulin and in some studies prevented a rise in serum thyroid-stimulating hormone. None of the intervention trials recorded an excess frequency of thyroid dysfunction in contrast to observational studies. A pooled analysis of two RCTs which measured cognitive function in school-age children showed modest benefits of iodine supplementation on perceptual reasoning (standardised mean difference (SMD) 0.55; 95% CI 0.05, 1.04; PZ0.03) and global cognitive index (SMD 0.27; 95% CI 0.10, 0.44; PZ0.002) with significant heterogeneity between studies. Conclusion: Iodine supplementation improves some maternal thyroid indices and may benefit aspects of cognitive function in school-age children, even in marginally iodine-deficient areas. Further large prospective controlled studies are urgently required to clarify these findings and quantify the risk/benefits of iodine supplementation in regions previously believed to be iodine sufficient such as the UK.

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“…However, no such synergistic effects were found in a randomized trial with concomitant iodine and selenium supplementation in a New Zealand population of similar selenium and iodine status (37). Furthermore, the iodine fortification program in Denmark was associated with an increase in the TPO-Ab positivity prevalence (38). An attenuating modulation of this effect by selenium is conceivable, due to its potential to decrease thyroid antibodies in autoimmune thyroid disease (39).…”

Section: Discussionmentioning

confidence: 98%

Does selenium supplementation affect thyroid function? Results from a randomized, controlled, double-blinded trial in a Danish population

Winther¹,

Bonnema²,

Cold³

et al. 2015

European Journal of Endocrinology

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Objective: Selenium is present in the active site of proteins important for thyroid hormone synthesis and metabolism. The objective of this study is to investigate the effect of selenium supplementation in different doses on thyroid function, under conditions of suboptimal dietary selenium intake. Design: The Danish PREvention of Cancer by Intervention with SElenium pilot study (DK-PRECISE) is a randomized, doubleblinded, placebo-controlled trial. A total of 491 males and females aged 60-74 years were randomized to 100 mg (nZ124), 200 mg (nZ122), or 300 mg (nZ119) selenium-enriched yeast or matching yeast-based placebo tablets (nZ126). A total of 361 participants, equally distributed across treatment groups, completed the 5-year intervention period. Methods: Plasma samples were analyzed for selenium and serum samples for TSH, free triiodothyronine (FT 3 ), and free thyroxine (FT 4 ) at baseline, and after 6 months, and 5 years of supplementation. Results: Plasma selenium concentrations increased significantly and dose-dependently in treatment groups receiving selenium (P!0.001). Serum TSH and FT 4 concentrations decreased significantly and dose-dependently by 0.066 mIU/l (PZ0.010) and 0.11 pmol/l (PZ0.015), respectively, per 100 mg/day increase, with insignificant differences between 6 months and 5 years. No significant effects were found for FT 3 and FT 3 :FT 4 ratio. Conclusions: In euthyroid subjects, selenium supplementation minutely and dose-dependently affects thyroid function, when compared with placebo, by decreasing serum TSH and FT 4 concentrations. Based on these findings, selenium supplementation is not warranted under conditions of marginal selenium deficiency. However, a role for selenium supplementation in the treatment of autoimmune thyroid diseases is still unresolved.

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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

Cited by 141 publications

References 34 publications

Improvement in iodine status of pregnant Australian women 3years after introduction of a mandatory iodine fortification programme

Improvement in iodine status of pregnant Australian women 3years after introduction of a mandatory iodine fortification programme

THERAPY OF ENDOCRINE DISEASE: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis

Does selenium supplementation affect thyroid function? Results from a randomized, controlled, double-blinded trial in a Danish population

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