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Supplements Can Contain Excess Iodine

-- A. Agrawal, PhD

Wednesday, January 21, 2009

WEDNESDAY, Jan. 21 (HealthDay News) -- Some over-the-counter supplements contain high levels of iodine that may interfere with radioiodine treatment in patients with thyroid cancer, according to a case study published in the Jan. 22 issue of the New England Journal of Medicine.

Seth M. Arum, M.D., from the University of Massachusetts Memorial Medical Center in Worcester, Mass., and colleagues describe the case of a 55-year-old man who needed to be treated with radioiodine after removal of a large papillary thyroid carcinoma that had metastasized to the lymph nodes.

Before beginning radioiodine treatment, the researchers found that his urinary iodine was elevated to 394 micrograms per liter, and remained high even after a low-iodine diet and furosemide treatment. Although the patient believed that none of the 22 supplements he was taking was responsible, further investigation showed that a kelp-enriched selenium supplement was the source of the excess iodine. After the patient stopped taking all supplements and maintained a low-iodine diet, his urinary iodine fell to 36 micrograms per liter.

"The iodine content of kelp is highly variable, and it is likely that the iodine levels in different batches of kelp-enriched selenium are also highly variable," Arum and colleagues write. "Although it is not routine to assess urinary iodine concentrations in patients receiving radioiodine, we emphasize the need for physicians to review patients' medications and dietary habits carefully to prevent ingestions of hidden sources of iodine."

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Specialties Cardiology
Diabetes & Endocrinology
Internal Medicine
Family Practice

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