a test used to assess the ability of the adrenal cortex to produce cortisol. Serum cortisol is measured before and then 30 minutes after an intramuscular injection of 250 µg tetracosactide (Synacthen), an analogue of ACTH. The adrenal glands are considered to be inadequate if there is a low baseline concentration of cortisol or the rise is less than a certain predefined amount.
Medical dictionary. 2011.