THE RELATIONSHIP OF HYPERTHYROIDISM TO MYASTHENIA GRAVIS*

Abstract

MUSCULAR weakness and fatigability may be prominent in uncomplicated hyperthyroidism. The mechanism is not clear but it seems likely that there is direct embarrassment of muscle metabolism. Certainly creatinuria is marked, and muscle isolated from a hyperthyroid animal uses much more oxygen than normal (1). In addition, however, there are a number of well defined neuromuscular disorders which may coexist with hyperthyroidism and which may be modified by it. A study of the interrelationships between these conditions might well shed light upon them, or even more important—upon the manifold problems of muscular fatigue in man. The following neuromuscular disorders which may appear with the hyperthyroid state are described briefly in order to emphasize the wide variety of mechanisms that may be involved: 1. Exophthalmic ophthalmoplegia (2, 3). This consists in progressive protrusion of the eyeballs due to a dystrophic process affecting the extraocular muscles. There is edema, fatty infiltration and swelling o...