An insulin tolerance test is not without considerable risks, and should only be undertaken by an experienced doctor who understands the complications. It is usually only performed in tertiary centres.
The principle is to give an insulin bolus, and measure the response in terms of growth hormone, cortisol and prolactin at regular intervals. It is very important to also monitor the blood glucose, since hypoglycaemia can be severe and may need treatment.
Growth hormone deficiency is suggested by a poor response to the insulin stimulus.
Note that before the test is begun a normal cortisol must be demonstrated.
*Note that reference ranges for tests may vary between laboratories. Also growth hormone stimulation tests can be difficult to interpret; the cut-off value for 'normal' growth hormone response is not universally agreed, and the hormone levels achieved by provocation depend on the age and pubertal stage of the child (as well as on the stimulus and assay used) (1).
Reference:
(1) Drugs and Therapeutics Bulletin (2002), 40 (3), 17-20.
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