Iodine deficiency may eventually lead to hypothyroidism, which causes a variety of symptoms including fatigue, weight gain, weakness and/or depression. Interestingly, iodine deficiency can also cause hyperthyroidism, a condition characterized by weight loss, rapid heart beat, and appetite fluctations.Severe iodine deficiency during pregnancy or infancy causes cretinism, a condition characterized by hypothyroidism leading to failure of the thyroid gland and/or severe mental retardation, stunted physical growth, deafness, and spasticity. If discovered in its initial stages, cretinism can be corrected with iodine supplementation.