Just as hypothyroidism slows down the body's functioning, hyperthyroidism speeds it up, causing accelerated heart rate, high blood pressure, and other concerns. Hyperthyroidism occurs when the thyroid is overactive, producing more thyroid hormone than is necessary. In some patients, antithyroid drug treatment for 12 to 18 months will result in prolonged remission of the disease, particularly if the disease is relatively mild when treatment is begun. Antithyroid drugs work for about 20% to 30% of patients.

These drugs make it more difficult for your thyroid to use the iodine it needs to produce thyroid hormone, resulting in a decrease in thyroid hormone production. When the disease is mild, or occurs in children or young adults, or needs to be promptly controlled (as with elderly patients whose heart disease puts them at risk from the increased heart rate associated with Grave's disease), the first main treatment approach is often a course of antithyroid drugs such as propylthiouracil (PTU) or methi-mazole (Tapazole). These drugs can be useful in rapidly reducing potentially dangerous symptoms until treatment has taken effect. Regardless of the method of treatment eventually used, as a first course of action a doctor may initially recommend that you take a beta-adrenergic blocking drug - also known as a beta blocker - such as atenolol (Tenormin), nadolol (Corgard), metoprolol (Lopressor), or propranolol (Inderal) to block the action of circulating thyroid. (Note: Because radioactivity can potentially damage the unborn or breast-feeding infant's thyroid gland, this procedure is not done during pregnancy or breast-feeding.) This overactivity is a hallmark of Graves' disease. A radioactive picture of the thyroid that is made by ingesting radioactive iodine by mouth may also be taken to see if the thyroid gland is overactive. Additionally, the thyroid-stimulating antibodies (TSAb) or thyroid-stimulating immunoglobulin (TSI) in your blood may also be measured to diagnose Graves' disease, the autoimmune condition that frequently causes hyperthyroidism.

So anything lower than the 0.3 to 0.5 range would likely be diagnosed as hyperthyroid. As of spring 2003, most American laboratories had a normal range from around 0.5 to 5.5; however, recent laboratory guidelines and standards have recommended that the normal range be revised to 0.3 to 3.0. A diagnosis is usually made by a thyroid-stimulating hormone (TSH) test. Hyperthyroid patients often have an enlarged thyroid, which can be felt by a doctor upon examination. Being hypothyroid and taking too much thyroid medication. Thyroiditis, an inflammation of the thyroid that makes the thyroid overactive. A goiter, nodule, or nodules that have caused the thyroid to inappropriately produce too much thyroid hormone. Autoimmune Hashimoto's disease, a characteristic of which is a short spurt of overactivity before the thyroid shifts into underactivity. Hyperthyroidism may be caused by; An autoimmune disease (Graves' disease) that has caused the immune system to attack the thyroid.