THE VALUE OF THE GLUCOSE TOLERANCE TEST, THE INSULIN TOLERANCE TEST, AND THE GLUCOSEINSULIN TOLERANCE TEST IN THE DIAGNOSIS OF ENDOCRINOLOGIC DISORDERS OF GLUCOSE METABOLISM1

Abstract

CARBOHYDRATE METABOLISM is influenced by I many tissues, notably pancreatic islets, adrenal medulla, adrenal cortex, anterior pituitary, muscles and liver. As an aid in the diagnosis of various diseases, it has for a long time been useful to study the glucose content of the blood. Thus, the determination of this under fasting conditions may at once give the clue to the diagnosis. In many instances, however, because of compensatory adjustments the fasting level is normal in spite of a definite disturbance in the sugar metabolism (e.g., mild diabetes) and it is necessary to subject the sugar-regulatory mechanism to some selected strain in order to elicit an abnormality. What strain one chooses naturally should depend on what disorder one suspects. For example, if looking for hypo-insulinism one would test the ability of the body to adjust to an alimentary hyperglycemia, that is one would perform the ordinary sugar tolerance test. If it turned out that the patient had a decreased responsiveness to hyperglycemia, that is the curve was delayed in its fall—the findings would be consistent with hypoinsulinism although there would be other possibilities which could be tested by subjecting the mechanism to other strains (see below). It was the purpose of these investigations, which will be reported more fully elsewhere (1), to study the additional usefulness in endocrine diagnosis of two other types of sugar curves, the “combined glucose-insulin test” and the “insulin tolerance test.”