USMLE Step 1 Adrenal Disorders practice questions
Adrenal disorders on USMLE Step 1 center on excess or deficiency of cortisol, aldosterone, and adrenal androgens/catecholamines, and on tracing each clinical picture back to a specific enzymatic or feedback defect. High-yield entities include primary adrenal insufficiency (Addison disease), congenital adrenal hyperplasia, Cushing syndrome (ACTH-dependent vs. ACTH-independent), primary hyperaldosteronism (Conn syndrome), and pheochromocytoma. Mastery requires linking the hypothalamic-pituitary-adrenal axis, steroidogenesis pathway enzymes, and receptor-level mechanisms to the resulting electrolyte, blood pressure, and physical exam findings.
A 34-year-old woman comes to the office because of a 4-month history of fatigue, weight loss, and craving for salty foods. Physical examination shows darkening of the skin creases of her palms and hyperpigmentation of the buccal mucosa. Serum sodium is 129 mEq/L and serum potassium is 5.6 mEq/L. Serum cortisol is low and does not increase after administration of cosyntropin. Which of the following is the most likely mechanism of this patient's skin findings?
A female newborn is noted to have clitoromegaly and partial fusion of the labioscrotal folds at birth. On day 10 of life, she develops vomiting, poor feeding, and lethargy. Serum sodium is 128 mEq/L, serum potassium is 6.4 mEq/L, and serum 17-hydroxyprogesterone is markedly elevated. Which of the following enzymes is most likely deficient in this infant?
A 45-year-old woman is evaluated for a 6-month history of weight gain, easy bruising, and new-onset hypertension. Examination shows central obesity, a dorsocervical fat pad, and violaceous abdominal striae. Morning plasma ACTH is undetectable, and a 6-cm mass is found in the left adrenal gland on CT. Which of the following is the most likely explanation for this patient's low ACTH level?
A 40-year-old man has recurrent episodes of pounding headache, palpitations, and profuse sweating lasting 20-30 minutes. During one episode in the office, his blood pressure is 210/120 mm Hg. Plasma free metanephrines are markedly elevated, and CT shows a 4-cm right adrenal mass. Which of the following is the most likely cell of origin of this patient's tumor?
A 50-year-old man with hypertension resistant to three antihypertensive medications is found to have a serum potassium of 3.0 mEq/L and serum bicarbonate of 30 mEq/L. Plasma aldosterone concentration is elevated and plasma renin activity is low. CT shows a 1.5-cm left adrenal nodule. Which of the following is the most likely mechanism of this patient's hypokalemia?
Adrenal Disorders, answered
How do I quickly distinguish 21-hydroxylase, 11-beta-hydroxylase, and 17-alpha-hydroxylase deficiency on Step 1?
Check virilization and blood pressure together: 21-hydroxylase deficiency causes virilization with salt wasting (hypotension, hyperkalemia); 11-beta-hydroxylase deficiency causes virilization with hypertension (from accumulated deoxycorticosterone); 17-alpha-hydroxylase deficiency causes hypertension with sexual infantilism and no virilization, because androgen and cortisol synthesis are both blocked while mineralocorticoid precursors build up.
What is the fastest way to tell Cushing disease from adrenal Cushing syndrome from ectopic ACTH?
Start with the ACTH level: low/suppressed ACTH points to an autonomous adrenal source (adenoma or carcinoma), while high ACTH points to a pituitary corticotroph adenoma (Cushing disease) or an ectopic ACTH-secreting tumor such as small cell lung carcinoma. A high-dose dexamethasone suppression test can then separate the two ACTH-dependent causes, since a pituitary source is more likely to show partial suppression than an ectopic source.
Why does Addison disease cause hyperpigmentation but secondary adrenal insufficiency does not?
Hyperpigmentation depends on high levels of POMC-derived peptides, which only occurs when the pituitary is trying to drive a failing adrenal gland (primary insufficiency). In secondary adrenal insufficiency, the defect is at the pituitary or hypothalamus, so ACTH/POMC production is low rather than elevated, and hyperpigmentation does not occur.
Is pheochromocytoma the same tumor as paraganglioma?
No. Both arise from neural crest-derived chromaffin tissue and secrete catecholamines, but pheochromocytoma specifically refers to a tumor within the adrenal medulla, while paraganglioma arises from extra-adrenal sympathetic or parasympathetic ganglia. Step 1 tests this distinction mainly at the level of anatomic origin rather than clinical presentation, since both can cause similar catecholamine-excess symptoms.
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