[Discordance between the short and standard metyrapone tests in isolated corticotropin insufficiency]

A 71-year-old man presented with clinical and common biological features of secondary adrenal insufficiency. Basal ACTH level was in the normal range. As it has been previously reported in ACTH deficiency, cortisol response to ACTH-test was normal. A single-dose metyrapone test, performed to confirm the diagnosis of adrenal insufficiency, gave unexpectedly normal results. However 11-desoxycortisol (compound S) response to standard-metyrapone test was subnormal ascertaining the diagnosis of ACTH-deficiency. Thus normal responses to single-dose metyrapone test do not imperatively exclude secondary adrenal failure.