WBR0224

Author	[[PageAuthor::Mugilan Poongkunran M.B.B.S [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Primary Care Office
Sub Category	SubCategory::Endocrine
Prompt	[[Prompt::A 58 yr old postmenopausal woman comes to the clinic for weight gain for the past 2 years. She is a known diabetic and hypertensive on metformin, hydrochlorthiazide and atenolol. She also complaints of tiredness and weakness while climbing stairs and combing. Her weight is 200lbs, height is 5.2” inches, BP: 130/80, HR: 90/min. On physical examination, her extremities are thin when compared to the trunk and her face is round and plethoric. Her abdomen is distended with violaceous striae and there is mild proximal weakness of her lower extremities. Her 24 hr urinary cortisol is three times above the normal and high dose dexamethasone suppression test failed to lower the cortisol levels. Plasma ACTH levels are undetectable. What is the best next step in diagnosis?]]
Answer A	AnswerA::CT of the chest
Answer A Explanation	AnswerAExp::'''Incorrect''' : CT chest is to look for ectopic source of ACTH producing tumour. With undetectable ACTH, this option is ruled out.
Answer B	AnswerB::MRI of the brain
Answer B Explanation	AnswerBExp::'''Incorrect''' : MRI of the brain is to look for pituitary dependent Cushing’s syndrome ( Cushing disease), where ACTH will be elevated or normal.
Answer C	AnswerC::CT of the abdomen
Answer C Explanation	AnswerCExp::'''Incorrect''' : Though CT and MRI are both of equal sensitivity and specificity, MRI is more preferable as it helps in characterization of adrenal tumors.
Answer D	AnswerD::MRI of the abdomen
Answer D Explanation	AnswerDExp::'''Correct''' : MRI of the abdomen is the best option of investigation for adrenal tumors.
Answer E	AnswerE::Inferior petrosal sinus sampling.
Answer E Explanation	AnswerEExp::'''Incorrect''' : Inferior petrosal sampling is required to differentiate ectopic ACTH from pituitary ACTH Cushing’s syndrome.
Right Answer	RightAnswer::D
Explanation	[[Explanation::This patient has the features of Cushing’s syndrome: hypertension, central obesity, muscle wasting, thin skin with purple striae, psychological disturbances, hirsutism, moon facies, and “buffalo hump.” Examination reveals depression, oligomenorrhea, growth retardation, proximal weakness, acne, excessive hair growth, symptoms of diabetes (2° to glucose intolerance), and ↑ susceptibility to infection. Increased urinary cortisol, non suppressible DEXA test and undetectable ACTH is more suggestive of adrenal etiology. The best next step is imaging. CT and MRI are both of equal sensitivity and specificity. However MRI is more useful for further characterization of adrenal tumors. Educational Objective: References: ]]
Approved	Approved::Yes
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