THE CHANGE IN THYROIDAL I131CONTENT BETWEEN 8 AND 48 HOURS AS AN INDEX OF THYROID ACTIVITY

Abstract

THE of thyrotoxic subjects differs from that of euthyroid subjects not only in the rate of uptake of the I¹³¹, but also in the time of reaching the maximum uptake (Fig. 1) and in the rate of the subsequent release. We have found that the change in thyroidal I¹³¹ content between 8 and 48 hours after oral ingestion of I¹³¹ (hereafter called the “8–48 hour thyroidal I¹³¹ change rate”) affords a useful index of the activity of the thyroid gland. We report here a comparison of the 8–48 hour thyroidal change rate, the 8-hour thyroidal uptake and the 24-hour thyroidal uptake, all performed in the same group of patients. METHODS AND SUBJECTS “In vivo counting of the thyroid. This was carried out with an apparatus in which two lead-cathode Geiger tubes,¹ joined in parallel and with appropriate lead shielding, are placed in front of the patient's neck, 16½ inches away from the skin overlying the thyroid isthmus (1). A dose of 15 microcuries (μc.) was used for each tracer test.”