Iodine Needs in the Pregnant and Postpartum Woman - American ...

Iodine Needs in the Pregnantand Postpartum WomanAmerican Thyroid AssociationTask Force on Thyroidand Pregnancy

Increased thyroid hormone production (↑ 50%),:- Thyrotropic regulation by hCG- Estrogen-mediated TBG increaseIncreased Maternal Dietary Iodine Requirementsin PregnancyIncreasedrenal iodineclearance(↑ 30-50%)Iodide transferred to the fetus

Increased Dietary Iodine Requirementsin Lactation• Normal lactating breast ductsconcentrate iodide (via sodiumiodide symporter), secreting itinto milkTazebay et al Nat Med 2000; 6:859-60• Only source of iodine nutritionfor breastfed infants

Effects of Iodine Deficiency• Maternal Risks• Goiter• Hypothyroidism• Risks to Fetus/Child• Miscarriage• Stillbirth• Congenital anomalies• Perinatal and infant mortality• Cretinism• Reduced IQICCIDD/UNICEF/WHO

Iodine Deficiency and Reduced IQ• Worldwide, the leading cause of preventablemental handicap; 30 million children bornunprotected annuallywww.WHO.int/WHOSIS• Average 12 point IQ reduction in infants ofseverely iodine deficient womenM Qian et al. Asia Pac J Clin Nutr 2005;14:32-42.• Societal costs: A loss of 1 IQ point reduces thepotential income earning capacity of the childby 2.39%Lisa et al. Public Health Rep 2005; 120: 607–613.

Recommended U.S. Iodine IntakeAge GroupRecommendedI 2 intake (μg/day)Adults 150Pregnant womenLactating women220290Adolescents 150Children 1-8y, 9-13y, >14y 90, 130, 1500-6months & 7-12m 110 & 130Institute of Medicine 2001

Tolerable Upper Limit for Daily IodineIntakeAdults (including pregnancy) – 1100 ug/day“ the highest average daily nutrient intake levelthat is likely to pose no risk of adverse healtheffect to almost all individuals in the generalpopulation.”Institute of Medicine 2001

Population Urinary Iodine Values andIodine NutritionPopulation groupNon-pregnantadultsMedian Urinary IodineConcentration (μg/L)OptimalExcessive100-199 >299Pregnant Women 150-249 ≥500Lactating Women≥100WHO Public Health Nutr 2007

Median Urine Iodine Concentration (μg/L)Median U.S. Urinary IodineConcentrations: NHANES 1971-2004400350320300250Total200150145168 160MalesFemales1005001971-74 1988-94 2001-02 2003-04Hollowell et al. JCEM 1998; 83:3401-8; Caldwell et al.Thyroid 2005; 15: 692-9 & 2008;18:1207-14.

% of U.S. Population with Urinary Iodine

Percent with UI

National Academy of Science“Although iodide deficiency is believed to be rare inthe United States, some pregnant women may havea low iodide intake. The committee believes thatfurther research is needed to measure moreprecisely the extent of, and risk factors for, iodidedeficiency, particularly in pregnant women and theiroffspring. However, while studies are beingconducted, the committee emphasizes theimportance of ensuring that all pregnant womenhave adequate iodide intake and, as a first step,recommends that consideration be given to addingiodide to all prenatal vitamins.”National Research Council, Health Implications ofPerchlorate Ingestion, 2005

American Thyroid AssociationRecommendations 2006• “Until additional physiologic data areavailable to make a better judgment, theAmerican Thyroid Associationrecommends that women receive 150 mcgiodine supplements daily duringpregnancy and lactation and that allprenatal multivitamin/mineralpreparations contain 150 mcg of iodine.”Thyroid 2006;16:949-51

Proportion of U.S. Prenatal MultivitaminsContaining IodineNon-prescriptionprenatal multivitamins(n = 127)69%(n=87)containiodine28%(n=27)containiodinePrescription prenatalmultivitamins(n = 96)Leung et al. N Engl J Med 2009;360:939-40

Sources of Iodine in U.S. PrenatalMultivitaminsIodine from Kelp• Measured iodine content in 25 brands:33 – 610 mg/daily dose.• 14 had iodine levels 50% discordantwith labeled valuesPotassium Iodide• Mean measured iodine content per dailydose in 35 brands was 119.0 ± 13.6 (SE) mg,equivalent to 76% of the labeled KI.Leung et al. N Engl J Med 2009;360:939-40