WBR245
| Author | PageAuthor::Gerald Chi |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology, MainCategory::Physiology |
| Sub Category | SubCategory::Oncology |
| Prompt | [[Prompt::A 48-year-old female was admitted with a chronic watery diarrhea and occasional shortness of breath. She reports frequent abdominal tenderness and has lost 12 pounds of weight over the past 2 months. She also complains of intermittent facial flushings which fails to respond to aspirin. Physical examination is notable for hyperactive bowel sounds, hepatomegaly, and a holosystolic murmur at lower left sternal border intensified by applying pressure on her liver. Disclosure of which of the following substances in the urine would be diagnostic?]] |
| Answer A | AnswerA::Vanillyl mandelic acid (VMA) |
| Answer A Explanation | [[AnswerAExp::Incorrect Increased urinary levels of VMA are found in pheochromocytoma, which is a neuroendocrine tumor of the adrenal medulla. Typical symptoms of increased sympathetic tone include palpitations, diaphoresis, anxiety, headache, and refractory hypertension.]] |
| Answer B | AnswerB::5-hydroxyindoleacetic acid (5-HIAA) |
| Answer B Explanation | [[AnswerBExp::Correct 5-hydroxyindoleacetic acid (5-HIAA) is the metabolite of serotonin which is found in patients with carcinoid syndrome.]] |
| Answer C | AnswerC::Cross-linked N-terminal telopeptides (NTX) |
| Answer C Explanation | [[AnswerCExp::Incorrect N-terminal telopeptides are biomarkers indicating increased bone remodeling, which is commonly associated with hyperparathyroidism, Paget disease of bone, and hypercalcemia of malignancy.]] |
| Answer D | AnswerD::Cyclic adenosine monophosphate (cAMP) |
| Answer D Explanation | [[AnswerDExp::Incorrect Urinary cAMP levels are elevated in conditions of hyperparathyroidism and PTHrP-secreting cancers.]] |
| Answer E | AnswerE::Porphobilinogen (PBG) |
| Answer E Explanation | [[AnswerEExp::Incorrect Increased urinary porphobilinogen is associated with acute intermittent porphyria.]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient's symptoms are suggestive of carcinoid syndrome which is caused by excessive production of serotonin and histamine by neuroendocrine neoplasms most commonly found in the gastrointestinal tract. Valvular involvement, typically includes tricuspid insufficiency or pulmonic stenosis, occurs after the serotonin-secreting tumor has metastasized to the liver. Facial flushing seen in carcinoid syndrome is mediated primarily by vasodilatory actions of histamine, which is not affected by prostaglandin inhibition by aspirin. Pellagra may occur when tryptophan is depleted by accelerated synthesis of serotonin, which is converted to 5-hydroxyindoleacetic acid (5-HIAA) and excreted in the urine. Educational Objective: |
| Approved | Approved::No |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |