EVALUATION OF THE RELATIONSHIP BETWEEN LONG-ACTING THYROID STIMULATOR, CLINICAL AND BIOLOGICAL THYROTOXICOSIS AND EXOPHTHALMOS

Abstract

ABSTRACT Long-Acting Thyroid Stimulator (LATS) determinations were performed on the unconcentrated serum of 92 hyperthyroid patients, using the slightly modified method of McKenzie. A positive LATS response was found in 27 per cent of patients with active thyrotoxicosis, in 55 per cent of patients with residual hyperthyroidism after 131 iodine therapy, in 63 per cent of patients with progressive exophthalmos and in 4 of the 4 patients with pretibial myxoedema. In active thyrotoxicosis, the incidence of LATS was the same in the untreated patients (26%) as in the patients insufficiently treated with antithyroid drugs (27%). In untreated and insufficiently treated patients, exophthalmos, LATS and thyroglobulin antibodies (TGA) were more frequently found in the younger patients. There was a quantitative correlation between the response to LATS and pretibial myxoedema. No relation was found between level of LATS and the severity of ocular signs in progressive exophthalmos or between level of LATS and the biological parameters of the thyroid function in active thyrotoxicosis: cholesterol, PB127I, 131I uptake tests and PB131I. In view of these data, it seems that the relationship of LATS to thyrotoxicosis and/or exophthalmos cannot be considered as a directly causal factor.