Internal Medicine

P1: SBT

0521779407-02 CUNY1086/Karliner 0 521 77940 7 June 7, 2007 19:18

68 Adrenal Insufficiency

➣Low cortisol (<7 mcg/dL) with low or normal ACTH (0–50 pg/ml)

at 8 AM in secondary AI

■Specific Diagnostic Tests

➣Cosyntropin stimulation test: cortisol before, 30, 60 min after

Cosyntropin (250 mcg) IM or IV; post-Cosyntropin cortisol <20

mcg/dL suggestive of AI, always abnormal in primary AI, good

specificity but limited sensitivity in secondary AI

■Other Tests

➣Insulin tolerance test (gold standard for secondary AI): regular

insulin 0.1U/kg IV, with plasma cortisol, glucose at 15, 30, 45 min,

requires medical supervision, potentially dangerous in setting of

seizure history, CV disease, elderly

➣Metyrapone test (gold standard for secondary AI): 3 g metyrapone

at midnight with 8 AM serum cortisol, 11-deoxycortisol, and

plasma ACTH – rarely done, metyrapone may be difficult to

obtain

➣Anti-adrenal antibodies (antibodies directed against 21-hydro-

xylase in autoimmune primary AI)

➣Anterior pituitary function tests (TSH, free T4, prolactin, IGF-1)

Imaging

■CT or MRI of adrenals if indicated

■MRI or CT of sella if indicated

differential diagnosis

■Primary AI:

➣Autoimmune

➣Infectious: esp TB, fungal (esp. histoplasmosis), opportunistic

(CMV adrenalitis, M intracellulare)

➣Genetic (X-linked adrenoleukodystrophy)

➣Congenital adrenal hyperplasia

➣Adrenal hemorrhage

➣Metastastic malignancy, lymphoma

➣Infiltrative (amyloidosis, sarcoid)

➣Drugs: suramin, ketoconazole, etomidate, aminoglutethimide,

metyrapone, anticonvulsants (Dilantin, phenobarbital, rifam-

pin)

■Secondary AI:

➣Pituitary tumor, apoplexy, irradiation, parasellar tumors

➣Metastases to pituitary

➣Autoimmune (lymphocytic hypophysitis)