Iodine 131 therapy is the optimal treatment for hyperthyroidism in cats. It is the safest and most effective treatment currently available. A single dose of iodine 131 results in a rapid return to normal thyroid function in most cats. Surgical Treatment is limited to the removal of tumor tissue in the neck region and carries several risks. In addition to the anesthetic risk for older cats and the stress of surgery, there can be post-operative complications affecting surrounding structures. Damage to or removal of the parathyroid glands can cause hypocalcemia and can lead to seizures. Damage to regional nerves can also cause paralysis of the vocal cords. The estimated cost for surgery is between $900 and $1,400. In cases where one affected gland is removed, 70% of the cats develop tumors in the other gland or at other sites in the body. Medical Management does not cure the disease. To properly regulate hormone levels, anti-thyroid drugs must be given long term. If medication is stopped, hyperthyroid symptoms return. Undesirable side effects such as vomiting, itching, hair loss, and serious blood disorders can occur. Frequent blood chemistry monitoring and dose adjustment are required. The cost for medical therapy and monitoring often exceeds $1,000 per year.