Thyrotoxic Myopathy (Peculiarities on Clinical Diagnosis by Specific Pattern of Muscle Weakness and Atrophy without Reduction of Strength in Quadriceps Muscles and Some Remarks on Cause of Muscle Weakness)

Data on 263 patients (47 males and 216 females) with thyrotoxic myopathy (TM) have been studied. 151 patients were under the Kazakov’s personal observation and 112 cases were taken from the literature. The quantitative evaluation of frequency, level of weakness (and atrophy) of some muscles, the description of topography of muscular lesions at different phases of TM have been presented. An original pattern of muscular weakness and atrophy was established which allow to reveal myopathy at its early stage, even with the absence of obvious signs of thyrotoxicosis. This permits to reasonable respect thyrotoxicosis in many cases. The weakening of hormonal control of cAMP-dependent processes is probably the basic cause of muscular weakness and structural changes in skeletal muscles in thyrotoxic myopathy (TM).

Keywords: Thyrotoxic myopathy, thyrotoxicosis, skeletal muscle, pattern of muscle involvement, terminal motor innervation, motor unit potentials, cycle AMP system in muscle.