NEW YORK (Reuters Health) – The tincture of iodine for diagnostic imaging can damage the thyroid gland, which increases the risk of future disease, suggests a new study.
A U.S. team found that people with signs of thyroid disease were two to three times more likely than a control group to have performed an imaging study with tincture of iodine.
The dose of dye given during these tests exceeds several hundred times the recommended daily intake of 150 mcg.
“It’s a dose very, very high, actually exceeds the amount to which patients would be exposed,” said study co-author, Dr. Steven Brunelli’s Hospital Brigham and Women in Boston.
In the world each year are given about 80 million doses of iodine. This chemical affects the kidneys, but until now there was only anecdotal evidence that could also damage the thyroid. Therefore, doctors often fail to mention the possible adverse effects on the gland.
The results of Brunelli’s team published in Archives of Internal Medicine arising from 400 patients treated at the Hospital of Brigham and Women’s Hospital and Massachusetts General, and later developed hypothyroidism or hyperthyroidism.
The researchers compared this group with more than 1,400 other patients with normal thyroid function (control group).
Blood samples revealed that people with hyperthyroidism were twice as likely than the control group have performed a computed tomography (CT) or cardiac catheterization with iodine.
When considering patients with signs of thyroid disease, the relationship became even stronger and included hypothyroidism.
If this represents a cause and effect, means there would be one extra case of hyperthyroidism in 33 patients exposed to the dye and one per 36 hypothyroid patients.
In the study, hypothyroidism, but hyperthyroidism is corrected over time.
For Brunelli, the results should make doctors more cautious with the use of diagnostic imaging with dyes, but recommended that patients do not reject these studies when necessary to prevent thyroid disorders.
“All of these thyroid disorders can be treated,” he said.
Dr. Jeffrey A. Kline, who researches the effects of iodine, praised the study’s release, but noted some limitations.
“It tells us that the blood samples of some patients include abnormal values after (diagnostic imaging) but do not know exactly what he meant for patients,” said Kline, who directs studies emergentología Carolinas Medical Center in Charlotte, North Carolina.
Kline estimated that one in every 1,000 patients exposed to the dye develops a thyroid disorder so upset to see a doctor. So, he said, kidney damage from the dye occurs in one in 10 patients is a much bigger problem.
Moreover, imaging studies also expose patients to radiation doses, which would raise slightly the risk of developing cancer.