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Primary adrenal insufficiency — USMLE Step 2 CK MCQ

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HardInternal MedicinePrimary adrenal insufficiencyUSMLE Step 2 CK

A 45-year-old woman has fatigue, nausea, orthostatic hypotension, sodium 127 mEq/L, and glucose 61 mg/dL. MRI shows a pituitary macroadenoma. Morning cortisol is 2.1 µg/dL, free T4 is low, and TSH is inappropriately normal. She is not in shock. Which treatment should be initiated first?

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Correct answer: A — Begin hydrocortisone now, then add levothyroxine after glucocorticoid coverage

The best answer is “Begin hydrocortisone now, then add levothyroxine after glucocorticoid coverage”. The findings indicate secondary adrenal insufficiency and central hypothyroidism from pituitary disease. Glucocorticoid replacement must precede levothyroxine because thyroid hormone accelerates cortisol metabolism and increases metabolic demand, potentially precipitating adrenal crisis in an untreated cortisol-deficient patient. Fludrocortisone is usually unnecessary in secondary disease because aldosterone is preserved. Neither desmopressin nor delaying treatment for prolonged confirmatory testing addresses the immediate cortisol risk.

Reference: Endocrine Society guideline: primary adrenal insufficiency. https://www.endocrine.org/clinical-practice-guidelines/primary-adrenal-insufficiency