I. Purpose

The purpose of this guideline is to assist nuclear medicine practitioners in recommending, perform-ing, interpreting and reporting the results of thyroid uptake measurements. II. Background Information and Definitions Thyroid uptake determination is the measurement of the fraction of an administered amount of ra-dioactive iodine that accumulates in the thyroid at selected times following ingestion. Thyroid uptake can also be determined using intravenously admin-istered Tc-99m pertechnetate and a gamma camera. In this document, hyperthyroidism refers to an ex-cess of circulating thyroid hormone due to an over-active thyroid gland as well as due to other causes. III. Common Indications A. Assist in determining the amount of I-131 to be administered to patients for therapy of hyper-thyroidism due to Graves ’ disease or toxic nodu-lar goiter. The uptake should be performed as close in time as possible to the treatment. B. Differentiate subacute or painless thyroiditis and factitious hyperthyroidism from Graves ’ disease and other forms of hyperthyroidism. C. Assist in diagnosing and confirming diagnosis of hyperthyroidism. D. Measurement of uptake is of limited value in di-agnosing hypothyroidism