[Disorders of neuromuscular transmission in hyperthyroidism]

Using the method of supramaximal electrostimulation 35 hyperthyroid patients with signs of muscle weakness or muscular fatigability were investigated and in over half the cases (53.5%) disturbances of neuromuscular transmission were found using sufficiently sensitive methods of activation. In nearly 70% of the tested muscles stimulated at 10 Hz a fall of the amplitude of successive potentials was observed. The analysis of these results suggested the following conclusions: 1. Muscular fatigability in hyperthyroidism is reflected in electrophysiological findings. 2. A comparison of hyperthyroidism with myasthenia showed that similarities and differences exist in the electrophysiological findings between both groups. 3. An additional, besides disturbances of neuromuscular transmission, factor determining muscular fatigibility in hyperthyroidism is probably damage to the muscle fibre.