Radioisotopic evaluation of the thyroid and the parathyroids.

Since the inception of the discipline of nuclear medicine, thyroid evaluation and therapy with radioactive isotopes have remained an important and constant component of thyroidology. Parathyroid scintigraphy with 201Tl/99mTc subtraction has been a more recent and also very useful addition in the assessment of hyperparathyroidism, particularly at reoperation. The radioactive iodine uptake test gives important metabolic information on thyroid function in such diverse disease states as hyperthyroidism, hypothyroidism, the thyroiditides, and thyroid carcinoma. Thyroid scintigraphy is also a key contributor to the assessment of patients with hyperthyroidism or with single versus multiple thyroid nodules, those with a history of head and neck irradiation during childhood, and those requiring diagnostic follow-up studies with 131I after total thyroidectomy for differentiated thyroid carcinoma. Each of these topics is reviewed and expanded on in this article, with a diversity of illustrative scans provided to complement the discussion.