Thyroid function tests. Selective use for cost containment.

Clinicians often obtain a variety of thyroid function tests in patients suspected of having thyroid disease when only a few are necessary to adequately establish a diagnosis and do follow-up. For hyperthyroidism and hypothyroidism, measurement of serum T4 is the best screening test. The serum T3 resin uptake test should be added with women suspected of being hyperthyroid because of the changes produced by pregnancy or estrogen-containing contraceptives. Various imaging techniques, including RAI, ultrasound, CT, and MRI, are often used for differentiating benign or cystic thyroid nodules from malignant or solid ones. Each of the available techniques has a different cost, and each is most suitable for a particular disorder. Special tests (eg, TRH testing and measurement of serum TBG) should be added to the basic screening tests only for questionable cases to differentiate diagnostic possibilities or confirm an uncertain diagnosis.