Solitary Hyperfunctioning Thyroid Nodules

The thyroidal uptake and distribution of I131 were studied in 15 patients with clinically solitary nodules in the thyroid. In each patient the nodule was hyperfunctioning and accounted for almost all the activity; 9 of the patients were euthyroid, 5 were thyrotoxic, and 1 was in a borderline state between euthyroidism and thyrotoxicosis. In each of the patients studied after administration of triiodothyronine or thyroid-stimulating hormone, regardless of whether the patient was euthyroid or thyrotoxic, no nodule was suppressed by triiodothyronine, but the nonfunctioning thyroid outside the nodule was always responsive to thyroid-stimulating hormone. This suggests that such nodules elaborate a hormone which indirectly or directly suppresses the remainder of the thyroid, and that the nodules are autonomous since they are suppressed neither by their own hormone nor by exogenous triiodothyronine.