Long-acting thyroid stimulator (LATS) in toxic nodular goitre, toxic adenoma and Graves' disease.

Abstract

ABSTRACT The long-acting thyroid stimulator (LATS) was determined by means of the McKenzie assay in 68 patients with hyperthyroidism. The patients were classified into the following groups: Group 1. Graves' disease (diffuse goitre with hyperthyroidism with or without exophthalmos). Of the 35 patients tested 25 (71 %) were LATS-positive. Group 2. Graves' disease with nodular goitre (nodular goitre with hyperthyroidism and with exophthalmos). The present series includes only 4 such patients, although this combination is by no means uncommon in Finland. Two of the patients were LATS-positive. It has been suggested that these patients represent Graves' disease superimposed upon endemic nodular goitre. Group 3. Toxic nodular goitre. The present series comprises 23 patients with toxic multinodular goitre, of whom 10 (44%) were LATS-positive. In view of the findings on thyroid palpation, on thyroid scintigraphy, the presence or absence of LATS in the blood and some other criteria, these patients can be divided into two categories, (a) one with Graves' disease superimposed upon nodular goitre of endemic origin (see group 2) and (b) the other with classical multinodular goitre. Analysis of the scintigrams showed that in some patients (with either exophthalmos or LATS in the blood and nodular goitre = Graves' disease + nodular goitre) it was not the nodules that were activated but the paranodular tissue, a finding which gave a scintigram typical of patients with classical Graves' disease. In some LATS-positive cases, however, some nodules were also activated to the same extent. The difference between these scintigrams and those typical of classical multinodular goitre is particularly stressed since in Finland »toxic nodular goitre« is the prevailing type of hyperthyroidism. Group 4. Single toxic adenoma. Two patients out of 6 were LATS-positive. This is in contrast to the findings of other authors according to which LATS has never been found in patients with toxic adenoma. A hypothesis is put forward that in these patients subclinical Graves' disease (LATS in the blood) coincided with a primarily autonomous, hyperactive but not necessarily toxic single thyroid adenoma, which was more susceptible to the stimulating activity of LATS than the surrounding tissue.