Serum Iodine Is Correlated with Iodine Intake and Thyroid Function in School-Age Children from a Sufficient-to-Excessive Iodine Intake Area

Tingkai Cui; Wei Wang; Wen Chen; Ziyun Pan; Shu Gao; Long Tan; Elizabeth N Pearce; Michael B Zimmermann; Jun Shen; Wanqi Zhang

doi:10.1093/jn/nxy325

Serum Iodine Is Correlated with Iodine Intake and Thyroid Function in School-Age Children from a Sufficient-to-Excessive Iodine Intake Area

J Nutr. 2019 Jun 1;149(6):1012-1018. doi: 10.1093/jn/nxy325.

Authors

Tingkai Cui^{1

2

3}, Wei Wang^{1

2

3}, Wen Chen^{1

2

3}, Ziyun Pan^{1

2

3}, Shu Gao^{1

2

3}, Long Tan^{1

2

3}, Elizabeth N Pearce⁴, Michael B Zimmermann⁵, Jun Shen^{1

2

3}, Wanqi Zhang^{1

2

3

6}

Affiliations

¹ School of Public Health, Tianjin Medical University, Tianjin, China.
² Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin, China.
³ Tianjin Center for International Collaborative Research in Environment, Nutrition and Public Health, Tianjin, China.
⁴ Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, MA.
⁵ The Human Nutrition Laboratory, Swiss Federal Institute of Technology, Zürich, Switzerland.
⁶ Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.

PMID: 31070733
DOI: 10.1093/jn/nxy325

Abstract

Background: An alternative feasible and convenient method of assessing iodine intake is needed.

Objective: The aim of this study was to examine the utility of serum iodine for assessing iodine intake in children.

Methods: One blood sample and 2 repeated 24-h urine samples (1-mo interval) were collected from school-age children in Shandong, China. Serum free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), thyroglobulin (Tg), total iodine (StI), and non-protein-bound iodine (SnbI) concentrations and urine iodine (UIC) and creatinine (UCr) concentrations were measured. Iodine intake was estimated based on two 24-h urine iodine excretions (24-h UIE). Associations between serum iodine and other factors were analyzed using the Spearman rank correlation test. Receiver operating characteristic (ROC) curves were used to illustrate diagnostic ability of StI and SnbI.

Results: In total, 1686 children aged 7-14 y were enrolled. The median 24-h UIC for the 2 collections was 385 and 399 μg/L, respectively. The median iodine intake was estimated to be 299 μg/d and was significantly higher in boys than in girls (316 μg/d compared with 283 μg/d; P < 0.001). StI and SnbI were both positively correlated with FT4 (ρ = 0.30, P < 0.001; and ρ = 0.21, P < 0.001), Tg (ρ = 0.21, P < 0.001; and ρ = 0.19, P < 0.001), 24-h UIC (ρ = 0.56, P < 0.001; and ρ = 0.47, P < 0.001), 24-h UIE (ρ = 0.46, P < 0.001; and ρ = 0.49, P < 0.001), urine iodine-to-creatinine ratio (ρ = 0.58, P < 0.001; and ρ = 0.62, P < 0.001), and iodine intake (ρ = 0.49, P < 0.001; and ρ = 0.53, P < 0.001). The areas under the ROC curves for StI and SnbI for the diagnosis of excessive iodine intake in children were 0.76 and 0.77, respectively. The optimal StI and SnbI threshold values for defining iodine excess in children were 101 and 56.2 μg/L, respectively.

Conclusions: Serum iodine was positively correlated with iodine intake and the serum FT4 concentration in children. It is a potential biomarker for diagnosing excessive iodine intake in children. This trial was registered at clinicaltrials.gov as NCT02915536.

Keywords: children; iodine; iodine intake; serum iodine; thyroid function.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Biomarkers / blood
Child
China
Cross-Sectional Studies
Female
Humans
Iodine / administration & dosage*
Iodine / blood*
Iodine / urine
Male
Nutritional Requirements
Nutritional Status
Thyroid Function Tests
Thyroid Gland / physiology*
Thyroid Hormones / blood
Thyroxine / blood

Substances

Biomarkers
Thyroid Hormones
Iodine
Thyroxine

Associated data

ClinicalTrials.gov/NCT02915536