THE AUGMENTED INSULIN TOLERANCE TEST FOR DETECTING INSULIN RESISTANCE

Abstract

SUMMARY 1. An augmented insulin tolerance test and its normal response is described; after a standard preparation, 11·1 u. of soluble insulin/m.2 of body surface is injected intravenously, and the level of blood sugar followed for 2 hr. 2. The degree of insulin resistance, in such states as acromegaly, can be indexed by the sum of the blood sugar values, as mg./100 ml., at 60, 90 and 120 min. after insulin. In normal subjects the mean 'insulin resistance index' was 92 (range 62–142). The test is valid only if the fasting blood sugar is normal. 3. Results are reported in: (a) twelve 'untreated' acromegalics in all of whom the test showed an abnormal insulin resistance index (mean 173 and range 144–228); (b) fourteen treated acromegalics (after gold-198 or yttrium-90 implants), in eight of whom the insulin resistance index was normal, although only five were judged to be in full clinical remission; (c) twelve subjects with gross but 'simple' obesity in whom the test results were nearly as abnormal as those of the 'untreated' acromegalics (mean insulin resistance index 159 and range 119–221). 4. The test can be used to assess the 'activity' of acromegaly and its response to treatment, provided the subject is not also grossly obese.