Evaluating iodine deficiency in pregnant women and young infants—complex physiology with a risk of misinterpretation

• Published in: Public health nutrition Vol. 10; no. 12A; pp. 1547 - 1552
• Main Authors: Laurberg, P, Andersen, S, Bjarnadóttir, R I, Carlé, A, Hreidarsson, AB, Knudsen, N, Ovesen, L, Pedersen, IB, Rasmussen, LB
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.12.2007
• Subjects: Adult; Blood; Cord blood; Creatinine; Estimates; Female; Fetal Blood - chemistry; Fetuses; Food; Humans; Infant; Infant, Newborn; Infants; Investigations; Iodine; Iodine - blood; Iodine - deficiency; Iodine - metabolism; Iodine - urine; Laboratory tests; Literature reviews; Male; Nutrient deficiency; Nutrition; Nutrition Assessment; Nutritional Status; Physiology; Population studies; Pregnancy; Pregnancy Complications - blood; Pregnancy Complications - epidemiology; Public health; Sensitivity and Specificity; Thyroglobulin; Thyroid; Thyroid gland; Thyroid Gland - physiology; Thyroid-stimulating hormone; Thyrotropin - blood; Thyroxine; Thyroxine - blood; Triiodothyronine - blood; Urine; Central America; Infants; Urinary iodine; Iodine Pregnant women; Deficiency Thyroid-stimulating hormoneThyroglobulin; Assessment
• ISSN: 1368-9800; 1475-2727
• DOI: 10.1017/S1368980007360898

Objective: To review methods for evaluating iodine deficiency in pregnant women and young infants and to discuss factors to be considered in the interpretation of their results. Design: Review of the literature regarding the various methods available for assessing iodine status. Setting: Population surveys and research studies. Subjects: Pregnant women and young infants. Results: Several factors to consider when assessing iodine status in pregnant women and young infants include: 1) the urinary iodine (UI) concentration (μg l-1) is not interchangeable with 24 h UI excretion (μg per 24 h); 2) the concentration of iodine in a spot or casual urine sample cannot be used to diagnose iodine deficiency in an individual; 3) a moderate fall in the concentration of serum free T4 during pregnancy is not a sign of maternal iodine deficiency; 4) an increase in the concentration of serum thyroglobulin (Tg) during pregnancy is not a sign of maternal iodine deficiency; 5) a higher concentration of TSH and Tg in cord blood than in maternal blood is not a sign of iodine deficiency in the mother or neonate; and 6) thyroid function in a full-term foetus, a neonate or a small child is not more sensitive to a mild iodine deficiency than in the mother. Conclusions: If the iodine status of pregnant women and small children is not to be misjudged, the above six factors need to be taken into account.