The term "hyperthyroidism" encompasses a heterogeneous group of disorders, all characterized by elevated levels of thyroid hormones in the blood. Since Graves' disease is the most common cause of hyperthyroidism, the following discussion will concentrate on that disorder.

Initial Visit

Medical History.--A detailed medical history will usually provide the clinician with sufficient clues to suggest the diagnosis of hyperthyroidism. Patients should be asked about nervousness, fatigue, palpitations, exertional dyspnea, weight loss, heat intolerance, irritability, tremor, muscle weakness, decreased menstrual flow in women, sleep disturbance, increased perspiration, increased frequency of bowel movements, change in appetite, and thyroid enlargement. Patients should also be asked about photophobia, eye irritation, diplopia, or a change in visual acuity. In individuals in whom Graves' disease is not obvious, questions regarding recent iodine exposure, prior or current thyroid hormone use, anterior neck pain, pregnancy, or history of goiter should be included. A family history of thyroid disease should be sought.

Physical Examination.--An appropriately thorough physical examination should be performed during the initial evaluation. Aspects of the examination to be stressed include weight and height, pulse rate and regularity, blood pressure, cardiac examination, thyroid enlargement (diffuse or nodular), proximal muscle weakness, tremor, an eye examination (for evidence of ophthalmopathy), and a skin examination (for pretibial myxedema). Older individuals may have few if any symptoms and signs of hyperthyroidism except for weight loss and cardiac abnormalities, in particular atrial fibrillation and/or congestive heart failure.

Laboratory Evaluation.[ref. 1]--True hyperthyroidism must be distinguished from "euthyroid hyperthyroxinemia," which may be caused by certain drugs, nonthyroidal illness, and a variety of other, less common factors. Specific tests to establish the diagnosis of hyperthyroidism include an estimate or direct measurement of free thyroxine (T[sub]4[/sub]) (which is elevated in hyperthyroidism), as well as a serum thyroid-stimulating hormone (TSH) measurement (which is suppressed in hyperthyroidism). The TSH level should be measured in an assay that is sensitive enough to clearly discriminate euthyroid from hyperthyroid individuals. When the free T[sub]4[/sub] level (estimate) is elevated in a clinically hyperthyroid patient, a serum TSH level that is not suppressed should alert the clinician to the possibility of hyperthyroidism due to a TSH-producing pituitary adenoma. If hyperthyroidism is confirmed, other tests may be performed according to the clinical situation. These may include total triiodothyronine (T[sub]3[/sub]), thyroid autoantibodies, and a radioactive iodine uptake test. The latter test should be obtained if the diagnosis of Graves' disease is not secure; this may be the case in patients with "painless," postpartum, or subacute thyroiditis who will have low, rather than elevated, radioactive iodine uptake values.[ref. 1] Specific treatment should generally be withheld until the biochemical diagnosis and cause of hyperthyroidism are confirmed. In most instances, symptomatic relief can be obtained with beta-adrenergic-blocking drugs while the patient is undergoing additional diagnostic testing.