Increased pertechnetate and radioiodine uptake in the thyroid gland with subacute thyroiditis and concurrent Graves'...

A 61 years old woman presented with low grade fever and weight loss for a month. Thyroid function tests showed hyperthyroidism: increased technetium-99m pertechnetate ((99m)Tc O(-)4) and radioiodine ((131)I) uptake and elevated thyroid stimulating hormone receptor antibodies (TSHRAb). She also had high erythrocyte sedimentation rate. Fine-needle aspiration (FNA) biopsies of left thyroid lobe revealed subacute thyroiditis (SAT). Simultaneous occurrence of SAT and Graves' disease (GD) was diagnosed. The patient was in good physical condition after two doses of betamethasone and daily administration of low dose antithyroid drugs.

This case indicated that the measurement of TSHRAb is useful in understanding the clinical course of patients with SAT when thyroid function tests including the (99m)Tc and (131)I uptake are not compatible with the diagnosis. In such cases, GD should be suspected. The mechanism of high (99m)Tc and/or (131)I uptake in patients with simultaneous SAT and GD may be due to the inflammatory process which was detected by FNA in a small part of the left thyroid lobe inducing the stimulating effects of elevated TSHRAb on the undamaged follicular cells.