Estimation of Iodine Intake from Various Urinary Iodine Measurements in Population Studies

Vejbjerg, Pernille; Knudsen, Nils; Perrild, Hans; Laurberg, Peter; Andersen, Stig; Rasmussen, Lone Banke; Ovesen, Lars; Jørgensen, Torben

doi:10.1089/thy.2009.0094

Cited by 168 publications

(168 citation statements)

References 31 publications

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“…However, as discussed, this could have limited our ability to find correlations between UIC and Tg, except in the countries with the lowest iodine intake, where the day-to-day UIC might have been less variable. Also, we did not measure creatinine in the urine samples and express the iodine concentration per unit of creatinine, which might have improved our individual classification of iodine status (44). The use of DBS simplifies the collection and transport of samples, which can lower field costs compared with the use of serum assays.…”

Section: Discussionmentioning

confidence: 99%

Dried Blood Spot Thyroglobulin as a Biomarker of Iodine Status in Pregnant Women

Stinca

Andersson

Weibel

et al. 2016

The Journal of Clinical Endocrinology &Amp; Metabolism

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Context: Thyroglobulin (Tg) could be a sensitive biomarker of iodine nutrition in pregnant women (PW). A dried blood spot (DBS) assay would simplify collection and transport in field studies. Objectives: Our aims were to (1) establish and test a reference range for DBS-Tg in PW; (2) determine whether co-measurement of Tg antibodies (Abs) is necessary to define population iodine status. Design, Setting, and Participants: Standardized cross-sectional studies of 3870 PW from 11 countries. For the DBS-Tg reference range, we included TgAb-negative PW (n = 599) from 3 countries with sufficient iodine intake. Main Outcome Measures: We measured the urinary iodine concentration and DBS thyroidstimulating hormone, total thyroxin, Tg, and TgAb. Results: In the reference population, the median DBS-Tg was 9.2 g/L (95% confidence interval, 8.7 to 9.8 g/L) and was not significantly different among trimesters. The reference range was 0.3 to 43.5 g/L. Over a range of iodine intake, the Tg concentrations were U-shaped. Within countries, the median DBS-Tg and the presence of elevated DBS-Tg did not differ significantly between all PW and PW who were TgAb-negative. Conclusions: A median DBS-Tg of 10 g/L with <3% of values 44 g/L indicated population iodine sufficiency. Concurrent measurement of TgAb did not appear necessary to assess the population iodine status.

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Section: Discussionmentioning

confidence: 99%

Dried Blood Spot Thyroglobulin as a Biomarker of Iodine Status in Pregnant Women

Stinca

Andersson

Weibel

et al. 2016

The Journal of Clinical Endocrinology &Amp; Metabolism

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“…For the individual subjects, we used the estimated 24-h iodine excretion, adjusted for age and gender, as an indicator for the iodine status. The estimated 24-h urinary iodine excretion was calculated as follows: iodine (mg/l)/creatinine (g/l)!expected 24-h creatinine (g/day) (18,19,20). A large Belgian population study provides data on the expected creatinine excretion per individual, taking age and sex into account (21).…”

Section: Laboratory Methodsmentioning

confidence: 99%

Longitudinal trends in thyroid function in relation to iodine intake: ongoing changes of thyroid function despite adequate current iodine status

Ven

Netea‐Maier

Ross

et al. 2014

European Journal of Endocrinology

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Objective: Several cross-sectional studies on populations with iodine deficiency showed that TSH-levels are negatively associated with age, while in populations with high iodine intake TSH is positively associated with age. The question is whether such an age-thyroid function relation is an ongoing process apparent also in longitudinal studies and whether it reflects an actual iodine deficiency or an iodine insufficiency in the past. Methods: In an area with a borderline iodine status in the past, we studied 980 participants of the Nijmegen Biomedical Study. We measured serum TSH, free thyroxine (FT 4 ), total triiodothyronine (T 3 ), peroxidase antibodies, and the urine iodine and creatinine concentration 4 years after our initial survey of thyroid function, in which we reported a negative association between TSH and age. Results: Within 4 years, TSH decreased by 5.4% (95% CI 2.5-8.3%) and FT 4 increased by 3.7% (95% CI 2.9-4.6%). Median urinary iodine concentration was 130 mg/l. Estimated 24-h iodine excretion was not associated with TSH, T 3 , change of TSH, or FT 4 over time or with the presence of antibodies against thyroid peroxidase. Only FT 4 appeared to be somewhat higher at lower urine iodine levels: a 1.01% (95% CI 0.17-1.84%) higher FT 4 for each lower iodine quintile. Conclusions: In this longitudinal study, we found an ongoing decrease in TSH and increase in FT 4 in a previously iodine insufficient population, despite the adequate iodine status at present. This suggests that low iodine intake at young age leads to thyroid autonomy (and a tendency to hyperthyroidism) that persists despite normal iodine intake later in life.

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“…The iodine (mg):creatinine (g) ratio was calculated by dividing urinary iodine by urinary creatinine and multiplying the result by 100. As we studied only Caucasian men of a particular age category (25-45 years), additional adjustment for sex, race, or age was not necessary (39). The intra-and interassay coefficients of variation were below 10% for all measurements.…”

Section: Biochemical Determinationsmentioning

confidence: 99%

Heredity and lifestyle in the determination of between-subject variation in thyroid hormone levels in euthyroid men

Roef¹,

Taes

Toye

et al. 2013

European Journal of Endocrinology

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Objective: Variation in thyroid hormone (TH) concentrations between subjects is greater than in a single subject over a prolonged period of time, suggesting an individual set point for thyroid function. We have previously shown that TH levels within normal range are associated with clinical indices such as bone mass, BMI, and heart rate. The aim of this study on young men was therefore to gain insight into the determinants of variation in TH levels among healthy subjects. Methods: Healthy male siblings (nZ941, 25-45 years) were recruited in a cross-sectional, populationbased study; a history or treatment of thyroid disease and thyroid auto-immunity were exclusion criteria. A complete assessment of TH status was performed (TSH, free thyroxine (FT 4 ), free triiodothyronine (FT 3 ), thyroperoxidase, and thyroglobulin antibodies, reverse T 3 (rT 3 ), thyroidbinding globulin (TBG), and urinary iodine levels). Genotyping was performed by TaqMan and KASP (KBiosciences) genotyping assays. Results: (F)T 4 , rT 3 , and TBG had heritability estimates between 80 and 90%. Estimates were lower for (F)T 3 (60%) and lowest for TSH (49%). Significant associations were observed between different single-nucleotide polymorphisms (SNPs) in the thyroid pathway and TSH, FT 4 , ratio FT 3 :FT 4 , and rT 3 . Nevertheless, these SNPs only explain a limited part of the heredity. As to age and lifestyle-related factors, (F)T 3 was negatively related to age and education level, positively to smoking and BMI (all P!0.0001) but not substantially to urinary iodine concentrations. Smoking was also negatively related to TSH and positively to FT 4 . Conclusion: Both genetic and lifestyle-related factors play a role in determining between-subject variation in TH levels in euthyroid young men, although genetic factors seem most important.

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Estimation of Iodine Intake from Various Urinary Iodine Measurements in Population Studies

Abstract: In studies of iodine intake, the correct choice of the method for collecting urine and the format for expressing the results of urine iodine measurement is essential to avoid misinterpretation of data on the iodine status of a population or individuals.

Cited by 168 publications

References 31 publications

Dried Blood Spot Thyroglobulin as a Biomarker of Iodine Status in Pregnant Women

Dried Blood Spot Thyroglobulin as a Biomarker of Iodine Status in Pregnant Women

Longitudinal trends in thyroid function in relation to iodine intake: ongoing changes of thyroid function despite adequate current iodine status

Heredity and lifestyle in the determination of between-subject variation in thyroid hormone levels in euthyroid men

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