Refinements to Assessment of Iodine Nutrition.

ABSTRACT

Objectives: The main target groups of iodine programs are pregnant women (PW) and nonpregnant women of reproductive age (NPW), yet surveys frequently focus on school age children (SAC). It is unclear whether median urinary iodine concentration (mUIC) in SAC can be used as a surrogate for PW and NPW. It is also unclear what range of iodine intake is adequate in SAC. The objectives of this research were to 1) Compare mUIC values in SAC with those in PW and NPW; and 2) determine if the current mUIC range for SAC is appropriate by assessing thyroglobulin (Tg), a functional biomarker of iodine status. Methods: 1) The Iodine Task Force (ITF) reviewed surveys where mUIC in SAC, PW, and NPW were available and compared iodine status across groups; and 2) for determining the adequate range of mUIC in SAC, the ITF analyzed and interpreted a multicenter study. Results: 1) When SAC had adequate or above adequate iodine status, PW were inadequate in 47% of the surveys. 2) In SAC, the two current WHO/UNICEF/ICCIDD mUIC categories for classification of iodine nutrition as "adequate" and "above adequate" could be combined into a single "adequate" range based on Tg results showing no negative effect on the thyroid at the current "above adequate" range. Conclusions: A number of refinements to the current global recommendations in assessing iodine status were identified, including the importance of including PW and/or NPW in population-based assessments, and reconsideration of current mUIC criteria for the classification of optimal iodine nutrition in SAC.