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.
1 Secondary Hyperthyroidism indicates that the dysfunction is caused by factors extrinsic to the thyroid gland (i.e., not due to a disorder in the gland). 2  In contrast, primary hyperthyroidism occurs when the dysfunction is caused by abnormal functioning of the thyroid gland itself. Secondary Hyperthyroidism indicates that the dysfunction is caused by factors extrinsic to the thyroid gland (i.e., not due to a disorder in the gland). 2  In contrast, primary hyperthyroidism occurs when the dysfunction is caused by abnormal functioning of the thyroid gland itself.