title: Associations between iodine intake, thyroid volume, and goiter rate in school-aged Chinese children from areas with high iodine drinking water concentrations.
abstract: Excessive iodine intake may have adverse effects on the thyroid, particularly in children, but the safe upper iodine intake concentration in children is unclear.
  
  
  
  We assessed the adverse effects of high iodine intake from iodine-rich drinking water on thyroid size in children by examining associations between thyroid volume (Tvol), total goiter rate (TGR), and iodine intake.
  
  
  
  In a multistage cross-sectional survey, we collected two 24-h urine samples on 2 nonconsecutive days and determined 24-h urinary iodine excretion, then calculated habitual daily iodine intake. Ultrasonographic Tvol was measured, and TGR was calculated based on international and Chinese reference ranges for Tvol in children.
  
  
  
  This study included 2089 children from Shandong province, where the median (IQR) drinking water iodine concentration was 183 μg/L (69-406 μg/L). The median (IQR) 24-h urinary iodine concentrations for the 2 collections were 381 μg/L (203-649 μg/L) and 398 μg/L (202-687 μg/L), respectively. The median (IQR) habitual daily iodine intake of children was 298 μg/d (186-437 μg/d). Tvols were slightly higher in boys than in girls (P = 0.035). The overall TGR was 9.7% and did not differ by sex. The TGR was ∼5% for children aged 7-10 and 11-14 y at iodine intakes of 200-249 and 250-299 μg/d, respectively. With the use of logistic regression and 2-step linear regression, a nonlinear association was observed between Tvol, TGR, and iodine intake, with a threshold intake of 150 μg/d.
  
  
  
  Tvol begins to increase in children when iodine intake is ≥150 μg/d, and the TGR exceeds 5% when daily iodine intake is ≥250 μg/d for children aged 7-10 y and ≥300 μg/d for children aged 11-14 y. Our findings suggest that 150-249 and 150-299 μg/d seem to be safe upper iodine intake ranges for children aged 7-10 and 11-14 y, respectively. This trial was registered at clinicaltrials.gov as NCT02915536.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Yalan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Shandong Institute for Endemic Disease Control and Research, Jinan, China.
authors.forename: Jianchao
authors.initials: J
authors.lastname: Bian
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
authors.affiliation: Shandong Institute for Endemic Disease Control and Research, Jinan, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Jiang
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Long
authors.initials: L
authors.lastname: Tan
authors.affiliation: Shandong Institute for Endemic Disease Control and Research, Jinan, China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, MA.
authors.forename: Elizabeth N
authors.identifier: 0000-0003-3799-0354
authors.initials: EN
authors.lastname: Pearce
authors.affiliation: Human Nutrition Laboratory, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland; and.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Zimmermann
authors.affiliation: Department of Statistics, Iowa State University, Ames, IA.
authors.forename: Alicia L
authors.initials: AL
authors.lastname: Carriquiry
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China; wqzhang@tijmu.edu.cn.
authors.forename: Wanqi
authors.identifier: 0000-0002-6044-1137
authors.initials: W
authors.lastname: Zhang
mesh_terms: D002648:Child; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D060766:Drinking Water / Q000737:chemistry*; D005260:Female; D006042:Goiter / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000009:adverse effects* / Q000652:urine; D008297:Male; D015995:Prevalence; D012016:Reference Values; D013961:Thyroid Gland / Q000187:drug effects*; D014131:Trace Elements / Q000008:administration & dosage / Q000009:adverse effects* / Q000652:urine
chemical_list: D060766:Drinking Water; D014131:Trace Elements; D007455:Iodine
keywords: children; thyroid volume; total goiter rate; urine iodine concentration; urine iodine excretion