Iodine in pregnancy, needs, impact and controversy

The American Thyroid Association has recommended that all pregnant and breastfeeding women in the U.S. should take daily supplements containing 150 mcg iodine.

However, a study conducted by researchers at Boston University Medical Center has found that only 51 percent of U.S. prenatal multivitamins contain iodine.

"Normal thyroid function in fetuses and breast-fed infants, which is dependent on sufficient intake of iodine, is crucial for a child's normal neurocognitive development," said Elizabeth N. Pearce, MD, assistant professor of medicine, in a research letter appearing in the February 26 issue of the New England Journal of Medicine (Vol. 360, No. 9).

According to the researchers, iodine deficiency affects more than 2.2 billion people worldwide and is the leading cause of preventable mental retardation. Over the last three decades, the iodine intake of U.S. women of childbearing age has decreased by more than half, and a subset of U.S. women of childbearing age may have mild iodine deficiency.

"Even mild iodine deficiency may have adverse effects on the cognitive function of children," said Dr. Pearce. "The measured iodine content of multivitamins with kelp as the iodine source was extremely variable, and often did not match labeled values," said Dr. Pearce. "Prenatal multivitamins containing potassium iodine were a more reliable source."

The iodine content of prenatal vitamins is not mandated in the U.S., noted the researchers, who suggest that manufacturers of prenatal vitamins in the U.S. should be encouraged to ensure that their products contain the amount of iodine recommended by the American Thyroid Association and to use only potassium iodine - which contains 76 percent iodine - to maintain consistency in iodine content.

Dr. Pearce will discuss "Iodine in Pregnancy: Needs, Impact and Controversy" at the American Thyroid Association's "Research Summit and Spring Symposium," held in Washington, DC April 16-17, 2009 at The Madison Hotel.

The American Thyroid Association (ATA) is the lead organization in promoting thyroid health and understanding thyroid biology. The ATA values scientific inquiry, clinical excellence, public service, education, collaboration, and collegiality. ATA members are physicians and scientists who work to enhance the understanding of thyroid physiology and pathophysiology, improve diagnosis and treatment of thyroid diseases, and promote the education of physicians, patients, and the public about thyroid cancer. Thyroid diseases are the most common disorders of the endocrine system, affecting almost 13 million Americans.