A number of symptoms and signs are well-established manifestations of thyroid dysfunction. Additional findings in patients' personal and family histories indicate increased risk of developing thyroid dysfunction. Risk factors identifiable in personal history include (1) previous thyroid dysfunction; (2) goiter; (3) surgery or radiotherapy affecting the thyroid gland; (4) diabetes mellitus; (5) vitiligo; (6) pernicious anemia; (7) leukotrichia (prematurely gray hair); and (8) medications and other compounds, such as lithium carbonate and iodine-containing compounds (eg, amiodarone hydrochloride, radiocontrast agents, expectorants containing potassium iodide, and kelp). Risk factors identifiable in the family history include (1) thyroid disease, (2) pernicious anemia, (3) diabetes mellitus, and (4) primary adrenal insufficiency.

Abnormal results in certain commonly obtained laboratory tests also suggest hypothyroidism or hyperthyroidism. Findings of these tests for hypothyroidism may include (1) hypercholesterolemia, (2) hyponatremia, (3) anemia, (4) creatine phosphokinase and lactate dehydrogenase elevations, and (5) hyperprolactinemia; and for hyperthyroidism, (1) hypercalcemia, (2) alkaline phosphatase elevation, and (3) hepatocellular enzyme elevation. Any of these clinical and laboratory findings justify thyroid function testing, particularly if they are sustained for 2 weeks or more, occur in combination, have not been present previously during documented euthyroidism, or occur in individuals with increased risk of thyroid disease.