Muscle weakness caused by an iodine-deficient diet: investigation of a nutritional myopathy.

Newborn rats raised on a commercially available iodine-deficient diet developed severe muscle weakness, affecting predominantly their proximal hind limbs, that electrophysiologically and morphologically was determined to be myopathic in type. Follow-up dietary studies, utilizing different combinations of vitamins, minerals, casein and elemental iodine, demonstrated that the myopathy was the result of a deficiency of multiple dietary constituents, particularly casein, and was not due to a deficiency of iodine alone. These findings were compared with those observed in earlier investigations of a variety of nutritional myopathies. In the laboratory study of animals raised on experimental diets, it becomes important to consider the possible contributions of multiple dietary deficiencies in the evaluation of any abnormalities found.