Growth stimulating antibodies in endemic goitre: a reappraisal

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Abstract
Previous studies, using a variety of methods, have reported growth-promoting immunoglobulins (IGs) in a large proportion of patients with endemic goitre. We sought to determine whether thyroid growth-promoting immunoglobulins (TGI) are present in the serum of Indian patients with endemic goitre. IgG was prepared by protein G-Sepharose affinity purification and added to FRTL-5 thyroid cells in the presence of suboptimal concentrations of TSH. We studied 30 sequential patients with endemic goitre and 16 euthyroid controls without a goitre from the same area. Two assays for thyroid cell growth were used: 3H-thymidine incorporation, and flow cytometric measurement of the proportion of cells in the S phase and G2/M phase of the cell cycle. Both assays were shown to detect growth produced by TSH and by thyroid stimulating antibodies in IgG preparations from 3 patients with Graves' disease. There was no significant increase in either 3H-thymidine incorporation or the distribution of cells in S or G2/M phase with IgGs from endemic goitre patients, and no difference between the effects of these IgGs and those from the normal subjects. Thyroid growth-promoting immunoglobulins cannot be detected in Indian patients with endemic goitre.