Other cells that contain hemoglobin include the A9 dopaminergic neurons in the substantia nigra, macrophages, alveolar cells, and mesangial cells in the kidney. In these tissues, hemoglobin has a non-oxygen-carrying function as an antioxidant and a regulator of iron metabolism.
The opposite is hypothyroidism, when the thyroid gland does not make enough thyroid hormone. Graves' disease is the cause of about 50% to 80% of case of hyperthyroidism in the United States. Other causes include multinodular goiter, toxic adenoma, inflammation of the thyroid, eating too much iodine, and too much synthetic thyroid hormone.
In normal people this would be an indication of low iodine levels causing the body to hang on to all iodine. Ordinarily the iodine would be used to make thyroid hormone, but in hypothyroidism it collects in the colloid and forms a goitre. Treatment: Thyroxin (thyroid hormone) will inhibit production of TSH and TRH. Hyperthyroid A hyperthyroid goitre is caused by over activation of the thyroid gland. This is usually caused by an autoimmune condition that is stimulating thyroid hormone production in absence of TSH (Grave's Disease).