Thyroid cancer and stealth iodine-containing drugs

A 55-year-old man treated for thyroid cancer was on a low-iodine diet as part of treatment, but his iodine levels of continued to increase.

A patient history published in The New England Journal of Medicine and reported in reveals an unexpected source of iodine among the 20 supplements he was taking.

It turns out that a selenium supplement he was taking contained kelp — a rich source of iodine. Stopping all 20 supplements resulted in a lowering of his thyroid blood levels to normal. More research narrowed the problem to a selenium product, which also included kelp (a source of iodine) that was not listed on the label.

Case solved.

But the problem continues.

“Dietary supplements can contain plant extracts, or even plant parts like kelp,” says Dr. Andrew Shao at the Council for Responsible Nutrition. “But it is not an inactive ingredient.”

The bottom line?
The authors concluded, “If you want to treat patients with radioactive iodine — if you want them to be on a low-iodine diet — you must be extremely inquisitive and cautious, and find out all the over-the-counter remedies they are taking.”

Here’s a list of drugs that contain iodine.

But these drugs aren’t the real problem. It’s all those drugs that contain iodine that we don’t know about.

And it’s not limited to supplements. As summarized in an earlier post, topically applied cosmetics can also have unintended consequences in high-risk people.

Healthcare professionals must inquire about CAM use, and patients must be forthcoming about their use of them.

1/25/09 19:10 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.