ITT is a test accepted as the gold standard in the evaluation of HPA axis and GH reserve.
However, it must be performed under the supervision of a physician and this test is contraindicated in patients with cardiovascular disease, cerebrovascular disease and epilepsy.
How is it done?
First of all, the vascular access is opened to the patient, who has been fasting for the night, in order to allow emergency intervention; 20 or 50% dextrose solutions are kept ready.
Blood sample is taken for basal values of glucose and cortisol (-15th minute) and then 0.1-0.15 U / kg i.v. bolus regular insulin is administered.
When the patient develops symptomatic hypoglycemia (which can be determined by neuroglycopenic symptoms and capillary blood), it is accepted as the 0th minute, the blood sample is taken and the test begins.
After that;
Blood samples are taken for glucose and cortisol values at 30, 60, 90 and 120. minutes. If symptomatic hypoglycemia does not develop within 45 minutes, the first dose may be given again.
The important point is that although the symptoms and hypoglycemia with capillary blood are accepted and the test is started, the test is not valid if the plasma glucose does not fall below 40 mg / dl (if there is no biochemical hypoglycemia in any minute).
Patients with severe symptoms of hypoglycemia and signs of neuroglycopenia can be given iv dextrose.
Evaluation: To be able to say that the hypothalamo-pituitary-adrenal axis is normal, the peak cortisol value after hypoglycemia should be 18 μg / dl and above.
