A 58-year-old female is complaining of weight gain for the past two years. She suspects a hormonal cause for her weight gain because she has not changed her activity or diet for the last several years. She also feels very tired and weak. She experiences difficulty in climbing the stairs and in combing her hair. She has mild hypertension and type II diabetes mellitus. She is currently on metformin, hydrochlorothiazide, and atenolol. She does not smoke cigarettes or drink alcohol. She had menopause when she was 48 years old. Her blood pressure is 130/70 mm Hg, heart rate is 88/min, and temperature is 98F (36.7C). She weighs 200 lbs, and is 5'2" tall (she was 5' 4" tall 5 years ago). Physical examination reveals a significantly overweight patient with prominent fat distributed in the trunk region. Her extremities seem thin when compared to her trunk. Her face is round and plethoric. She has a buffalo hump. She does not have any significant hirsutism or temporal balding. Her abdomen is distended and has wide, multiple, violaceous striae. There is mild proximal weakness of her lower extremities. The 24-hour urinary cortisol level is over three times above the upper limit of normal range. High-dose dexamethasone suppression test does not suppress the serum cortisol level. Plasma ACTH levels are undetectable. What is the next best step in the management of this patient?

Question

A 58-year-old female is complaining of weight gain for the past two years.  She suspects a hormonal cause for her weight gain because she has not changed her activity or diet for the last several years.  She also feels very tired and weak.  She experiences difficulty in climbing the stairs and in combing her hair.  She has mild hypertension and type II diabetes mellitus.  She is currently on metformin, hydrochlorothiazide, and atenolol.  She does not smoke cigarettes or drink alcohol.  She had menopause when she was 48 years old.  Her blood pressure is 130/70 mm Hg, heart rate is 88/min, and temperature is 98F (36.7C).  She weighs 200 lbs, and is 5'2" tall (she was 5' 4" tall 5 years ago).  Physical examination reveals a significantly overweight patient with prominent fat distributed in the trunk region.  Her extremities seem thin when compared to her trunk.  Her face is round and plethoric.  She has a buffalo hump.  She does not have any significant hirsutism or temporal balding.  Her abdomen is distended and has wide, multiple, violaceous striae.  There is mild proximal weakness of her lower extremities.  The 24-hour urinary cortisol level is over three times above the upper limit of normal range.  High-dose dexamethasone suppression test does not suppress the serum cortisol level.  Plasma ACTH levels are undetectable.  What is the next best step in the management of this patient?

Quizplus · Accepted Answer

Explanation: This patient has clinical features of Cushing's syndrome. She also has a significantly increased urinary cortisol level, nonsuppressible high-dose dexamethasone suppression test, and undetectable ACTH levels. All of these findings are highly suggestive of Cushing's syndrome secondary to an adrenal etiology. The next best step in the evaluation of this patient is to perform imaging of the adrenal glands. CT scan and MRI have almost equal sensitivity and specificity for adrenal tumors, although MRI scans are sometimes more useful for further characterization of adrenal tumors. (Choice A) MRI of the brain will not be useful because the ACTH level is suppressed. In pituitary-dependent Cushing's syndrome (Cushing's disease), plasma ACTH levels are normal or elevated. (Choice B) CT scan of the chest is also not required because her ACTH levels are undetectable. Chest CT scan is performed to look for ectopic sources of ACTH (ectopic ACTH syndrome). Patients with Cushing's syndrome due to ectopic ACTH production usually have higher plasma ACTH levels when compared to patients with Cushing's disease. (Choice D) The patient has features which are more suggestive of Cushing syndrome rather than simple obesity. Furthermore, she has lost significant height, which is very suggestive of vertebral compression fractures. Further evaluation is warranted to investigate the cause of her disease. (Choice E) Inferior petrosal sinus sampling is used to differentiate the source of ACTH production (pituitary versus ectopic.) It is not used in patients with undetectable ACTH levels. Educational Objective: Cushing syndrome with an adrenal etiology is biochemically characterized by a nonsuppressible high-dose dexamethasone suppression test and low plasma ACTH levels.

A 58-Year-Old Female Is Complaining of Weight Gain for the Past Two