In the ΓÇÿshortΓÇÖ tetracosactrin test, after taking a basal plasma cortisol sample, 250┬╡g tetracosactrin (Synacthen) is administered either intramuscularly or intravenously. Further samples for cortisol assay are taken at thirty and sixty minutes following the injection. This test is best performed at 0900 and the patient does not need to be fasting.
The normal increment in plasma cortisol is greater than 200nmol/1 (Fig. 9.8).
