ABSTRACT
The development of radiotracer methodology and the subsequent growth of in vivo nuclear medicine imaging techniques were immeasurably influenced by the unique avidity of the thyroid gland for iodine. The thyroid gland is the largest of the endocrine glands. It is H-shaped with two lateral lobes and an isthmus, and it is located at the third and fourth tracheal cartilage. The thyroid is grey or reddish brown in color and is highly vascular with the highest rate of blood flow per gm of tissue of any organ in the body. Physiologically and biochemically the thyroid gland is dedicated to the production of the protein thyroglobulin. To accomplish this, the thyroid avidly extracts iodine from the circulating vascular pool. Thyroid hormones are metabolically active, and are secreted into the circulation. The synthesis of thyroid hormones is regulated by thyroid stimulating hormone from the pituitary gland. Thyroid hormone affects activity of virtually every organ system within the body.
