MEDizzy - 54-year-old woman presents to the physician with diabetes

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ADRENAL DISORDERS

54-year-old woman presents to the physician with diabetes mellitus, osteoporosis, and hypertension. She has noted a recent weight gain and abdominal striae. Laboratory studies show a decreased ACTH level. A single mass is noted adjacent to the right kidney on abdominal CT scan. Neither low- nor high-dose dexamethasone suppresses the patient’s cortisol production. Which of the following is the most likely explanation for these findings?

ExplanationThe correct answer is A. The patient has signs and symptoms suggestive of hypercortisolism, also known as Cushing syndrome. Etiologies of hypercortisolism include a cortisol-producing adrenal adenoma, an ACTH-producing pituitary adenoma, paraneoplastic ectopic production of ACTH, and exogenous cortisol or ACTH administration. The dexamethasone suppression test can help distinguish between possible etiologies of hypercorticism. In normal individuals, low doses of dexamethasone suppress cortisol production. In patients with ACTH-producing pituitary adenomas, high doses of dexamethasone are needed to suppress cortisol production. In patients with adrenal adenomas or ectopic sources of ACTH, both low and high doses of dexamethasone fail to suppress cortisol production. Unlike patients with ectopic ACTH production, patients with an adrenal adenoma are expected to have low levels of ACTH due to negative feedback inhibition from the increased cortisol levels, as noted in this patient. Answer B is incorrect. Bilateral adrenal hyperplasia suggests increased stimulation of the adrenal glands due to increased ACTH production from either a pituitary adenoma or an ectopic ACTH source. Answer C is incorrect. Ectopic ACTH production is seen in paraneoplastic syndromes associated with bronchogenic cancer, pancreatic cancer, and thymomas. Bilateral adrenal hyperplasia and failed dexamethasone suppression are characteristics of ectopic ACTH production. A single mass noted on abdominal CT scan adjacent to a kidney is more suggestive of an adrenal adenoma than bilateral adrenal hyperplasia. Answer D is incorrect. Although exogenous corticosteroid administration, like adrenal adenomas, results in decreased levels of ACTH, a mass on abdominal CT scan would be unlikely in a patient with exogenous corticosteroid administration.