THE INSULIN-GLUCOSE TOLERANCE TEST. A MODIFIED PROCEDURE FOR THE DETECTION OF HYPOGLYCEMIA UNRESPONSIVENESS IN PITUITARY AND ADRENAL INSUFFICIENCY

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Abstract
A procedure is described for detecting hypoglycemia unresponsiveness which carries less risk than does the conventional insulin tolerance test and magnifies the differences between the normal and the hypoglycemia unresponsive patients. The mean response in 30 normal individuals to the intraven. admn. of 0.1 unit of insulin per kg. body wt. followed by 0.8 g. of glucose/kg. body wt. by mouth 30 min. later, consisted of a fall in the blood sugar to approx. 45% of the initial value followed by a prompt rise to a peak of 152% at 90 min. and a slow fall to the initial value by 180 min. In each of 13 curves from 3 patients with panhypo-pituitarism and 8 with Addison''s disease, there was a statistically significant decrease in the response to glucose after insulin, yielding relatively flat curves compared to the normals. In 8 patients in whom Addison''s disease or hypopituitarism were suspected but ruled out by other procedures, the insulin-glucose tolerance tests were not significantly different from normal. In one case in which hypopituitarism was not definitely ruled out, the response was equivocal. In a group of 9 patients with severe emaciation, 6 due to phychogenic causes and 3 due to organic disease, one patient with psychogenic vomiting fell clearly into the hypoglycemia-unresponsive group and one with anorexia nervosa was borderline. Five of 6 patients with myxedema had normal responses. The 6th fell into the hypoglycemia-unresponsive group and showed considerable improvement after thyroid therapy. Data were presented to suggest that this patient might have had adrenal insufficiency secondary to long-standing thyroid failure. Five patients with pituitary and adrenal overfunction syndromes showed a decreased fall in the blood sugar after insulin and either an exaggerated or a prolonged rise after glucose. Neither epinephrine nor cortical extract therapy restored to normal the response in the hypoglycemia-unresponsive group. Performance of the test after only a 5-hr. fast yielded a near normal response. The significance of the liver glycogen level in this test is emphasized.