Thyroid stimulating antibodies in sarcoidosis

Thyroid disorders, particularly euthyroid goiters and hyperthyroidism, can be observed in sarcoidosis. The aim of this study was to analyze the presence of thyroid stimulating antibodies (TSAb) in 21 patients with sarcoidosis. 12 patients out of 21 had simultaneous euthyroid goiter. The others were euthyroid and free of goiter.

The TSAb testing was carried out using the rat thyroid fragment perifusion technique. Thyroid response to IgG was determined by the mean rate of T4 release (R) during a 30-min perifusion and the secretion peak (Imax). Antibodies inhibiting TSH binding to its receptors were also looked for.

Ten patients were TSAb+ and eleven were TSAb-. There was no difference between the TSAb+ and TSAb- groups in the clinical parameters for sarcoidosis, nor in the number of goiters found (n = 6 for both groups). In 5 out of the 6 cases where goiter was present in the TSAb+ group it was homogeneous and diagnosed at the same time as or after the first signs of sarcoidosis, whereas in 5 out of the 6 cases of goiter in TSAb- patients, it was nodular, diagnosed before sarcoidosis in 3 of them, endemic in one of them, and familial in another. The search for antibodies inhibiting TSH binding to its receptors was negative in 10 out of 21 patients tested.

Although the presence of thyroid-stimulating antibodies in the serum of patients with sarcoidosis, found here for the first time, remains to be explained, it pleads in favor of the immunologic nature of the association of sarcoidosis with thyroid disorders.