Correlation between long-acting thyroid stimulator protector level and thyroid 131-I uptake in thyrotoxicosis.

Out of 50 consecutive untreated patients with diffuse toxic goitre 15 showed long-acting thyroid stimulator (LATS), 30 showed LATS protector only, and five showed neither. LATS protector was present in all the patients with LATS. Infiltrative ophthalmopathy was less common in patients with LATS protector only (40%) than in patients with LATS also (67%), but the difference was not significant. There was a correlation between LATS protector level and thyroid (131)I uptake rate factor (k(1)), the coefficient (r) being 0.68 (P < 0.001). LATS level showed no such correlation. The results support the hypothesis that LATS protector is a pathogenic thyroid stimulator in patients with diffuse toxic goitre.