[Radioimmunoassay in the diagnosis of atypical forms of thyrotoxicosis].

Fifty-six patients with "unmotivated" disorder of the cardiac rhythm were examined. A combined radionuclide study including a study of iodoabsorptive function with a standard technique, thyroid visualization and determination of the thyroxin triiodothyronine level in the blood serum with the radioimmunoassay using standart diagnostic kits, was conducted. Latent thyroid hyperfunction was revealed in 24 patients (42.8%). Study of iodoabsorptive function revealed pathological changes in 8 patients only, whereas radioimmunoassay revealed a significant elevation of the peripheral thyroid hormone level as compared to that of the control group in 24 patients. Change of the TSH level was not noted. The conclusion is that patients with "unmotivated" disorder of the cardiac rhythm often suffer from latent thyrotoxicosis which is the main etiological factor and trigger mechanism of arrhythmias. In such a situation they are the only clinical symptom of thyrotoxicosis that makes it possible to regard this form of disease as monosymptomatic. The early detection of the cause of cardiac rhythm disorder and the prescription of pathogenetic thyrostatic therapy resulted in the return of the cardiac cycle rate to normal in all the patients with sinus tachycardia and prevented relapses of the paroxysmal forms of rhythm disorder.