An interesting thing about millet is that the hulls and seeds contain small amounts of goiterogenic substances.  These substances limit the uptake of iodine to the thyroid and, in large amounts, these substances can cause goiter.  The substances are reduced through the hulling process.

Some researchers believe that the goiterogenic substances are reduced even further through cooking, while others believe that cooking and storing the millet in the refrigerator will actually increase the substances.

However, the goiterogenic substances are not unique to millet. In fact, common foods such as broccoli, cabbage, cauliflower, spinach, soy beans, and pears, also contain goiterogenic substances. There is no reason to be alarmed by these substances as a varied diet ensures that too much is not consumed. The nutritional value of millet and other foods outweighs the potential concerns. However, if you are hypothyroid, it is recommended that you eat three servings a day or less of these foods.