Ask the Doctor Hashimoto's and Extra Iodine
"I remain puzzled as to why I have Hashimoto's disease and wonder if it is at all possible that my long-term use of Betadine Shampoo (iodine shampoo) might have been a factor…I wonder if I should stop using the shampoo?" -- JB, Albany, NY
Iodine can have profound effects upon the thyroid. Small amounts of iodine such as that found in iodized salt are not problematic, but high exposures from Betadine shampoo, Betadine douches, Betadine or other iodine-containing antiseptics applied to the skin, kelp tablets, seaweeds, and some iodine-containing medications may all be problematic. The effects that high levels of iodine have on the thyroid and thyroid function depend upon the underlying thyroid problem.
In areas of the world where there is still iodine deficiency, iodine will reduce goiter and correct hypothyroidism. There is no iodine deficiency in the United States.
Untreated Hashimoto's disease is made worse by high doses of iodine. Goiters may enlarge and hypothyroidism may become more pronounced. However, once levothyroxine is started, there is little adverse effect from the addition of iodine.
Iodine may cause hyperthyroidism especially with patients with an underlying nodular goiter.
Interestingly, the addition of iodine to the food supply to prevent iodine deficiency goiter may well have increased the prevalence of Hashimoto's disease in the United States. Western Europe, which in general has not added iodine to the food supply, has a lower prevalence of Hashimoto's disease, but a higher prevalence of nodular goiter and follicular thyroid cancer.