Abstract
Considerable uncertainty exists with regard to the relation of thyroid function to carbohydrate metabolism. Some writers report a decrease, others, an increase of alimentary sugar tolerance after thyroidectomy in the dog. This confusion is due to several causes. Injury to the parathyroid bodies, which probably exert a different effect on metabolism from that of the thyroid, has frequently not been excluded. Previous experiments are open to other technical criticisms. The observations have been chiefly confined to urinary examinations.
Accordingly, a study of the blood sugar was made before and after thyroidectomy in a series of dogs. The operations were performed by Dr. J. E. Sweet. At least two parathyroids were isolated in each case. The wounds healed aseptically, and the dogs remained free from tetany. The blood sugar after thyroidectomy showed a marked decrease, averaging about 25 per cent. less than the normal value. The feeding of 6 1/2 grams of glucose per kilo in 40 per cent. solution before the operation to fasting animals showed the normal hyperglycemia to last three hours. After thyroidectomy, glucose fed under the identical experimental conditions, failed to raise the blood sugar to the level attained before the operation. The increase persisted however for an average of five hours. The urine remained free from glucose both before and after the operation with a single exception.
We have observed hypoglycemia in cretinism. It is present in myxedema, in Addison's disease, and after removal of the suprarenal bodies. Evidence is accumulating showing that a persistent low sugar content is a sign of insufficient internal secretion.
Quite aside from the doubtful question of whether increased alimentary tolerance to glucose can be demonstrated by an examination of the urine, these experiments show that there is less tendency to hyperglycemia on carbohydrate ingestion after thyroidectomy.
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