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Thyrotropin-receptor antibodies in patients with hyperthyroidism caused by Graves' disease inhibit thyrotropin secretion

(March 2002)

The background of the study. Patients who have hyperthyroidism have low serum thyrotropin (TSH) concentrations. When the patients are treated, serum TSH concentrations rise to normal or above. In some patients the recovery of TSH secretion is delayed. This study was done to determine if the TSH receptor-stimulating antibodies present in the serum of patients with hyperthyroidism caused by Graves' disease inhibit TSH secretion.

How the study was done. The effect of TSH receptor-stimulating antibodies on TSH secretion was studied in rats. The rats were given immunoglobulins (IgG) purified from the serum of a normal subject and patients with hyperthyroidism caused by Graves' disease; the latter had high serum concentrations of TSH receptor-stimulating antibodies. Blood samples were collected for measurement of plasma TSH 1, 2, 4, 8, 24, and 48 hours after the injections.

The results of the study. After the injections of IgG, the 48-hour mean plasma TSH concentration in the rats that received the IgG prepared from the serum of patients with hyperthyroidism was lower than in the rats that received the normal IgG.

The conclusions of the study. In patients with hyperthyroidism caused by Graves' disease, TSH secretion may be inhibited not only by the high serum T4 concentrations, but also by TSH receptor-stimulating antibodies.

The original article. Brokken LJS, Scheenhart JWC, Wiersinga WM, Prummel MF. Suppression of serum TSH by Graves' Ig: evidence for a functional pituitary receptor. J Clin Endocrinol Metab 2001;86:4814-7.