Thyroid tests: guide for primary care physicians.

Recent advances in thyroid testing have simplified the approach to the screening and diagnosis of thyroid disorders. The metabolic state is best determined by the serum free thyroxine and a sensitive assay for serum thyroid-stimulating hormone. The presence and nature of a goitre is assessed by clinical examination and, in the case of nodular thyroid disease, this examination can be supplemented by pertechnetate isotope scanning, ultrasonography, or fine needle aspiration biopsy. In most patients, these tests will identify the presence of and provide a guide to the diagnosis of thyroid disease. There is little need for radioactive iodine studies for diagnostic purposes.