Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1019 page)

   Insulin values are normal in

   Hypoglycemia associated with nonpancreatic tumors

   Idiopathic hypoglycemia of childhood, except after administration of leucine

   Circulating anti-insulin antibodies are often found in patients who have been treated with nonhuman forms of insulin. If present, these antibodies may interfere with the assay.

   For individuals who are significantly overweight, fasting insulin levels are typically somewhat higher than for adults of normal weight.

   Heterophilic antibodies in human serum can react with the immunoglobulins included in the assay components, causing interference with in vitro immunoassays. Samples from patients routinely exposed to animals or animal serum products can demonstrate this type of interference, potentially causing an anomalous result.

INSULIN TOLERANCE TEST

   Definition

   Insulin is administered, 0.1 U/kg body weight IV. A smaller dose should be used if hypopituitarism is suspected. IV glucose should be kept available to prevent severe reaction. Blood is obtained for serum glucose and cortisol assays (and for growth hormone [GH], if indicated) immediately before insulin is injected and 30 and 45 minutes thereafter. All patients, in whom adequate hypoglycemia is achieved, defined as 35 mg/dL or less should have some symptoms of hypoglycemia, either of sympathetic discharge or of CNS glucose deprivation, such as simply falling asleep.

   Use

   Assessing syndromes of extreme insulin resistance

   Crude classification of insulin sensitivity

   Assessing GH deficiency

   Interpretation