There are two types of ingredients in thyroid supplements. The first are ingredients that contain iodine. The ingredients listed may be kelp, bugleweed, or bladderwrack. Iodine is the critical component of a thyroid hormone molecule and iodine deficiency is known to cause thyroid dysfunction. However, iodine deficiency in the United States is extremely rare. This is because the American salt supply is fortified with iodine. In fact, the average American gets 300-500 mcg of iodine from their diet every day. This is double or triple the recommended daily allowance for iodine which is 150 mcg per day. If you do want to take an iodine supplement, a standard multivitamin which contains 150 mcg of iodine is sufficient.
Iodine is good for the thyroid, but more is not better. In fact, if you flood the thyroid with iodine, it will stop functioning. This is known as the Wolf-Chaikoff effect. In 1948, Drs. Jan Wolff and Israel Lyon Chaikoff at the University of California found that injections of iodine into rats completely stopped thyroid hormone production in the thyroid gland. In fact, the Wolff–Chaikoff effect is the reason potassium iodide is given to nuclear emergencies (which emit a lot of radioactive iodine).
The second and even more dangerous ingredient in thyroid supplements is from animal thyroid glands, primarily pig (porcine) and cow (bovine). These products are like prescription thyroid medications like Armour thyroid, Nature-throid and NP Thyroid, except they have zero quality control and may contain much more or much less than the dose listed on the label. If you want to take a glandular thyroid supplement, it is better to use one of the branded products with better quality control.
