The two major goals of thyroid function tests are to assess the amount of circulating thyroid hormone and to explain the findings obtained by physical examination of the gland.
Standard radioimmunoassays use one antibody, but supersensitive assays use two.
When the second antibody bears a fluorophor, an enzyme, or a chemiluminescent molecule, the test is designated as a third-generation TSH assay. The T 4 level is high in approximately 90 percent of hyperthyroid patients and low in approximately 85 percent of hypothyroid patients. This sensitivity should make the measurement of the T 4 level an excellent test for hyperthyroidism. T 4 level for hyperthyroidism is much lower. These factors include pregnancy, oral contraceptives, estrogens, acute infectious hepatitis, and genetic alteration.