A Case of Subacute Thyroiditis with Highly Positive Thyrotropin Receptor Antibodies and Normal Radioiodine Uptake

Abstract

In this paper, we report on a 40-year-old female with subacute thyroiditis (SAT) who showed high levels of TSH-binding inhibitory immunoglobulins (TBII) and thyroid-stimulation blocking antibodies (TSBAb) from the early stage of the disease. Thyrotoxicosis continued for 2 months and it was subsequently followed by severe hypothyroidism. Levothyroxine was then started. At that time, both TBII and TSBAb were still positive, but they disappeared 6 months later and she remained euthyroid thereafter without treatment. When she was in a thyrotoxic phase and had a suppressed TSH level, her 24-hour radioiodine uptake was not suppressed (11%), and thyroid scan showed partial suppression of uptake in the right lobe. These observations indicate that the presence of TSH receptor antibodies (TRAb) may have modified the changes in thyroid state and the course of SAT.

Scintigraphic Profile of Thyrotoxicosis Patients and Correlation with Biochemical and Sonological Findings

“…In our study, two patients had normal uptake, one patient had an uptake of 0.5% with USG showing no abnormality, on follow up without treatment he became clinically and biochemically euthyroid and was diagnosed to have thyroiditis. Resolving phase of thyroiditis can show normal vascularity and normal uptake as reported by Hisaoka T et al, [14]. Other patient had an uptake of 2.4% with borderline TSH values and minimal symptoms.…”

Subacute Thyroiditis with Highly Positive Thyrotropin Receptor Antibodies and High Thyroidal Radioactive Iodine Uptake

“…Thirty-two patients showed high titers of TRAband TSAb during the acute thyrotoxic phase of SATand four of them had high thyroidal RAIUor 99mTc uptake (7)(8)(9)(10)(11)(12). Histological examination of the thyroid gland, however, was reported in only three patients (7,10).…”