Dissociation of serum LATS activity and hyperfunction and autonomy of the thyroid gland in Graves' disease.

LATS was measured with the double isotope technique in IgG serum concentrates of 23 patients with Graves' disease before treatment and of 18 patients during treatment with carbimazole and triiodothyronine. LATS activity was present in 18 out of 23 patients before treatment (78%). When the second measurement was taken into account the incidence did increase to 95%. No difference could be found in the mean values of total thyroxine, thyroid 131-I uptake and thyroid weight of the group of LATS positive and LATS negative patients before treatment. Also no relation could be established between LATS activity and suppressibility of thyroid 131-I uptake during treatment. It was found that LATS positive patients who suppress during therapy have lower initial LATS blood levels than LATS positive patients who remain unsuppressed. It is concluded that it is more likely that LATS is a "marker" of Graves' disease rather than the cause of the hyperthyroidism.