Secondary adrenal insufficiency — The low dose test may have advantages over the standard high dose test in some clinical settings, in particular, for the diagnosis of recent onset ACTH deficiency (secondary adrenal insufficiency) and chronic partial pituitary ACTH deficiency .
In patients with recent onset ACTH deficiency (eg, within one to two weeks after pituitary surgery), the adrenal glands have not yet become completely atrophic and are still capable of responding to ACTH stimulation. Only insulin-induced hypoglycemia or the metyrapone test is completely reliable in these patients [38,39]. The practical clinical importance of this limitation is unclear.
However, the high-dose test performs well when it is performed at least four months after surgery, or nine months after radiation therapy. In one report, only 2 of 137 patients with 30-minute cortisol values between 18.2 and 22.7 mcg/dL (510 and 635 nmol/L) subsequently developed adrenal insufficiency .