Primary Adrenal Insufficiency:

 • ACTH stimulation test - Synthetic ACTH does not stimulate cortisol secretion because the dysfunctional adrenal cortex is already maximally stimulated by endogenous ACTH

 • Serum cortisol measured between 8 and 9 AM - Low

 • Plasma ACTH - Elevated, because feedback inhibition by adrenal cortisol is absent

 • Plasma aldosterone - Low in cases in which injury to the adrenal gland impacts both cortisol and aldosterone production

 • CRH stimulation test - Not necessary

 • Adrenal autoantibody tests - Serum tests that detect titers of adrenal autoantibodies are available for the confirmation of autoimmune-mediated primary adrenal insufficiency. The most commonly ordered is the 21-hydroxylase antibody test

Secondary Adrenal Insufficiency:

 • ACTH stimulation test - If the secondary adrenal insufficiency is mild or of recent onset, there is an increase in cortisol secretion; in chronic secondary adrenal insufficiency plasma cortisol is minimally increased after administration of ACTH because the adrenal cortex is atrophied from a long-term lack of stimulation by ACTH

 • Serum cortisol measured between 8 and 9 AM - Low

 • Plasma ACTH - Low, because the origin of the disorder is in the hypothalamus or pituitary

 • Plasma aldosterone - Often normal, although it may be depressed if there is significant atrophy of the adrenal glands as a result of chronic lack of stimulation by ACTH

 • CRH stimulation test - This test can distinguish between ACTH deficiency (from the pituitary) and deficiency of CRH (from the hypothalamus); plasma ACTH and cortisol are measured after administration of CRH; if secondary adrenal insufficiency is the result of a hypothalamic disorder, the CRH will produce an increase in plasma ACTH and cortisol

 • Adrenal autoantibody tests - Not necessary



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