Direct Evidence for Human Thyroidal Stimulation by LATS-Protector

Abstract

To examine the hypothesis that LATS-protector may cause thyroidal hyperfunction in Graves' disease, the effect of LATS-protector on the intracellular colloid droplet formation in human thyroid tissue was studied in vitro. The IgG's from 9 untreated patients with Graves' disease, 4 thyrotoxic patients who were being treated hut were still thyrotoxic, and 4 normal subjects not showing LATS were chosen to study the presence of LATS-protector and its human thyroid stimulating activity. LATS-protector was assayed as described by Adams with slight modifications. LATS-protector was demonstrated in the IgG's of 6 out of 9 untreated patients with Graves' disease. Their IgG significantly inhibited the inactivation of LATS by the thyroid extract, recovering approximately 30% of the LATS-potency. The IgG from the treated, but thyrotoxic patients or from the normal individual did not show such an inhibition. When sliced normal human thyroid tissue was incubated with the IgG from thyrotoxic patients, an obvious elevation in the number of intracellular colloid droplets was observed with all six IgG's which had shown LATS-protector activity. The IgG without LATS-protector activity did not cause an increase in the number of colloid droplets except for one IgG showing a questionable rise in colloid droplet counts. LATS-protector was almost as potent as standard LATS in inducing intracellular colloid droplets. Thus, our results demonstrated that both LATS-protector and LATS were potent thyroid stimulators, the former presumably being species-specific for human, while the latter was apparent in many mammalian thyroids.