'The thyroid cannot function without magnesium. Here is a list of very important functions of magnesium and how it relates to your thyroid gland health.
Magnesium is responsible for converting the inactive T4 thyroid hormone into the active form of T3. This is extremely important because the metabolism of your body cells are enhanced by T3, not inactive T4.
Magnesium deficiency is related to goiter, or an enlarged thyroid gland. Another important nutrient in preventing goiter is iodine, but magnesium is right there helping too.
Magnesium helps you to make more T4 in the thyroid gland. Without magnesium, many of the thyroid enzymes that make thyroid hormone simply could not function.'