Abstract
Motor unit estimating techniques have been employed as part of a comprehensive electrophysiological survey of peripheral nerve and muscle in 20 patients with thyrotoxicosis. In all patients there was evidence of a loss of operational motor units; the selective nature of this involvement suggested that the motoneurone soma was the site of the primary lesion. The reversible nature of the postulated motoneurone dysfunction was demonstrated by the increased motor unit counts in six patients who were studied again after treatment of their thyrotoxicosis.