Absouktely definitely YES. Underactive thyroid can cause a normal Depression ; it can complicate an existing Depression which arose for the usual reasons ( and treatment of the depression would be less effective if the thyroif insufficiency was not also dealt with ) and even with no actual Depression, some of the symptoms of Hypothyroidism can look and feel very like Depression. SO a good and careful diagnosis is needed, and combined treatment can be highly effective. Vitamins have no benefit in treating hypothyroidism, and even iodine ( the only relevant mineral ) on its own, as if the thyroid has insufficient thyroxine, it may not be able to handle dietary iodine usefully.