Variability of Daily Iodine Intake: The Effects of Intra- and Inter-individual Variability in Iodine Nutrition Studies

Study Overview
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Brief Summary
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Iodine status in populations is assessed using urinary iodine concentration (UIC) measured in spot urine samples. The iodine intake is classified as deficient, sufficient, or excessive iodine based on the median UIC (mUIC). However, this approach has limitations, as it does not quantify the prevalence of individuals with habitually deficient or excess iodine intakes. The EAR cut-point method has the potential to quantify prevalence of iodine deficiency and excess. However, little is known about the effects of the inter- and intra-individual variance of UIC. The aim of the study is to quantify the intra-individual variability in dietary iodine intake. The overall goal is to estimate the prevalence of iodine deficiency and excess in the study population and propose sample size recommendations for future iodine nutrition population studies. The results will provide evidence guiding international recommendations for iodine nutrition studies.

Official Title
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Variability of Daily Iodine Intake: The Effects of Intra- and Inter-individual Variability on Estimated Intake in Iodine Nutrition Studies

Conditions
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Iodine Deficiency

Intervention / Treatment
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* Other: No intervention


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Non-pregnant Non-lactating Non-smoking Residence in Switzerland ≥12 months Generally healthy No family history of goiter No exposure to iodine containing contrast agents during the last 12 months - Informed consent given Exclusion Criteria: Participant is not able to understand the study information or procedure, e.g. due to linguistic barriers

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 44 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Study group<br>We will collect two repeated spot urine samples, a DBS sample and obtain weight in all 600 study participants. In a randomly selected subsample (n=200) a third repeat spot urine sample and one 24 h urine will additionally be collected. | Other: No intervention<br>* This is an observational study and no interventions will be administered.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Estimated daily urinary iodine excretion | Estimated urinary iodine excretion (µg/day) will be obtained from urinary iodine concentration (UIC) and urinary creatinine concentration (UCC) measured in two repeat spot urine samples collected within 7 days | 7 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Measured daily iodine excretion | Measured daily iodine excretion (µg/day) will be obtained from urinary iodine concentration (UIC) and urine volume in a 24 h urine collection | 1 day | 
| Thyroid function test TSH | TSH concentration (mU/L) measured in dried blood spots | 1 day | 
| Thyroid function test total T4 | Total T4 concentration (nmol/L) measured in dried blood spots | 1 day | 
| Thyroid function test Tg | Tg concentration (µg/L) measured in dried blood spots | 1 day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Iodine, Urinary iodine concentration