When depot tetracosactrin is administered (1mg intramuscularly), the plasma cortisol levels at thirty and sixty minutes following the injection are virtually identical to those obtained with the short-acting preparation.
With primary and secondary adrenocortical failure, there may be no rise in cortisol at these times. With secondary failure, when blood samples are also taken at eight and twenty-four hours, the cortisol level usually rises in contrast to the lack of response in primary failure. Further injections of depot tetracosactrin can be given at intervals of twenty-four or forty-eight hours to restore the adrenal response to normal in secondary hypoadrenalism. Where depot preparations are not available, continuous intravenous infusions of ACTH may be given.
