Clinical significance of anti-TSH antibody in sera from patients with Graves’ disease and other thyroid disorders

Abstract

In a survey of patients having anti-TSH antibody (TSH Ab), data from 167 subjects were collected from 8 Japanese Institutions. They were divided into a high TSH Ab group consisting of 63 cases; since the means of assay was via a subnormal thyrotropin binding inhibitor immunoglobulin (TBII) assay, this group had TBII values less than −20%. An additional low TSH Ab group was made up of 104 cases. Out of a total of 11,211 patients, the incidence of TSH Ab for the high and low groups were 0.57% and 13.4%, respectively. More than 95% of these TSH Ab carriers had Graves’ disease or some other autoimmune thyroid disorder, and anti-thyroglobulin and anti-thyroid microsomal antibodies were detected similarly in both groups. It was significant that TSH receptor antibodies could also be detected in both groups, namely, thyroid stimulating antibody and long acting thyroid stimulator (LATS) in 4 of 9 patients in the high TSH Ab group and TBII in 55 of 104 in the low TSH Ab group, respectively. The high TSH Ab levels tended to persist, but 26% of cases showed disappearance or appearance of the antibody during the observation period. In one Graves’ patient, a moderate TBII activity (64.2%) was followed by markedly elevated TSH Ab (TBII: −83.4%) within 2 months. The TSH Ab in the low TSH Ab group disappeared in most cases. Also, fluctuations in TSH Ab did not always parallel those seen for TBII and reciprocal fluctuation pattern (transient or otherwise) were observed in 33%. In conclusion, anti-TSH antibody is produced frequently in patients with either Graves’ disease or some other autoimmune thyroid disorder. Interrelationship between this antibody and the TSH receptor antibody was not evident, and the reason for, and significance of, such antibody production remain to be elucidated.