A 42-year-old woman presents to the endocrinology clinic with a 6-month history of progressive facial plethora, easy bruising, proximal leg weakness, and irritability. Her blood pressure is 156/98 mmHg, and laboratory studies show serum potassium of 3.1 mEq/L. Screening tests reveal midnight salivary cortisol of 0.9 μg/dL (normal <0.1) and 24-hour urinary free cortisol of 295 μg/24h (normal <100). Plasma ACTH is 62 pg/mL (normal 10-46). A subsequent high-dose dexamethasone suppression test (8 mg overnight) shows morning serum cortisol of 3.2 μg/dL. Which of the following best explains these findings?
- A)Pituitary adenoma secreting ACTH (Cushing disease)GABARITO
- B)Ectopic ACTH-secreting neuroendocrine tumor
- C)Adrenal carcinoma producing cortisol and ACTH
- D)Primary bilateral adrenal hyperplasia
- E)Autonomous cortisol-secreting adrenal adenoma
Explicação
The key diagnostic finding is cortisol suppression to <5 μg/dL (actually 3.2 μg/dL) after high-dose dexamethasone (8 mg overnight). This suppression indicates ACTH-dependent Cushing syndrome with pituitary responsiveness to negative feedback, which is pathogno... Ver explicação completa e trilha adaptativa →