Inorganic phosphate response to intravenous glucose administration in progressive muscular dystrophy.

One outstanding biochemical finding in progressive muscular dystrophy (P.M.D.) is excessive creatinuria. Much of the experimental work on the disease therefore has been centered on creatinecreatinine metabolism. The conclusion has now been reached that the creatinuria in this condition arises from a normal endogenous creatine production in the presence of impaired removal of creatine from the blood stream as a result of the severe diminution of muscle mass (1). It has been furthermore inferred that such parts of the muscles which survive, remove creatine at a normal rate. This decrease in functional muscle mass appears to be a common feature in all distinct cases of progressive muscular dystrophy. In view of the well established role of carbohydrates as a source of energy in muscular activity, it is surprising that until now hardly any evidence has become available of a disturbance of carbohydrate metabolism in P.M.D. Abnormalities in glucose metabolism have been reported, including hypoglycemia, by McCrudden and Sargent (2, 3), reduced sugar tolerance by Janney, Goodhart, and Isaacson (4), and increased utilization of glucose by Magee (5), but more careful studies by Shank, Gilder, and Hoagland failed to confirm these results (6). In evaluating these negative findings of oral and intravenous glucose tolerance studies, it should be kept in mind that in the process of the removal of glucose from the blood stream in fasting subjects, the capacity of the liver is probably large enough to compensate for any deficiency on the part of the musculature. However, a crude measure of the respectiye portions removed by these tissues seems to be possible by the simultaneous recording of inorganic serum phosphate during the glucose tolerance test. Pollack and his coworkers (7) have demonstrated that phosphate is removed from a glucose and phosphate-containing perfusion fluid by the isolated hind limb, but not by the isolated liver of the dog. Recently, the estimation of a blood glucose and inorganic phosphate curve, after an oral or intravenous glucose load, has been used for diagnostic purposes in diabetes mellitus, various forms of liver dysfunction and in the study of glucose resorption in tropical sprue (Forsham and Thorn [8], Volk and Lazarus [9], and Fourman [10]). In the present report, this method has been used in the study of five cases of P.M.D., and the results have been compared to those obtained in normal subjects.