Electromyographic and endocrine studies in chronic thyrotoxic myopathy.

If the number of cases of a disease reported in the literature can be taken as an index of frequency, chronic thyrotoxic myopathy is a very rare disease. Its interest lies, however, not so much in its rarity as in the light it may throw on the inter-relationship of the endocrine glands and muscle function. In a previous paper (Sanderson and Adey, 1949) some aspects of this problem were reviewed and a case was reported in which the electromyographic findings were those typical of muscle dystrophy. Two further cases are presented here with the electromyographic findings, and with investigation of the function of the adrenal cortex in one case. The electromyograms give positive evidence of a muscular dystrophy of severe degree and show a return to the normal pattern after treatment of the thyrotoxicosis, thus making the diagnosis beyond doubt. The tests of adrenal cortical function were designed in rather a hurry and partly for this reason, but more especially because such tests are comparatively crude, the evidence for depressed function is inconclusive. That such a depression of function may occur in this disease is suggested by the necropsy findings of Thorn and Eder (1946) of atrophy of the glomerular layer of the adrenal cortex.