Insulin Tolerance Test

Indication: Diagnose adrenal insufficiency and growth hormone deficiency.

Procedure:

1. Insert saline lock to obtain serum blood samples and administer insulin.
2. Measure heart rate, blood pressure and blood glucose at 15 minute intervals.
3. Obtain human regular insulin.
4. Calculate dose of insulin for administration, 0.15U/kg.
5. Obtain a baseline serum cortisol (red top tube).
6. Administer correct dose of insulin, verifying amount with prescribing physician.
7. Observe patient for symptoms of hypoglycemia including, pallor, diaphoresis, heart palpitations, anxiety and blurred vision within 30 Ð45 minutes after the administration of insulin.
8. If patient is not symptomatic and the blood glucose is not less than 40, administer identical dose of insulin.
9. Once the blood glucose is less than < 40, obtain serum cortisol samples at 45, 60 and 90 minutes.
10. Once the blood glucose is < 40, obtain serum stat glucose level.
11. After completion of the test, administer orange juice to patient as necessary to elevate blood glucose to > 60.
12. If the patient exhibits symptoms of severe hypoglycemia and / or confusion at any time during the test, administer 1 ampule of D50 IV as a bolus injection.
13. If the patient becomes hypotensive in addition to other symptoms of severe hypoglycemia, administer Dexamethasone 4mg or 100mg of hydrocortisone hemisuccinate IV.
14. Document times of blood pressure, blood glucose, dosage of insulin and the collection of serum cortisol samples.
15. If it is necessary to obtain serum growth hormone levels (red top tube), collect at baseline, 30, 60, 90 and 120 after glucose level is < 40.

Interpretation: The administration of insulin should stimulate the adrenal glands to secrete cortisol and the pituitary gland to secrete growth hormone. Failure to respond appropriately to the insulin may suggest the need for hormone replacement.