]> 2026-07-31T16:29:26+00:00 WBR245 0 en Vanillyl mandelic acid 5-hydroxyindoleacetic acid (5-HIAA) Cross-linked N-terminal telopeptides (NTX) Cyclic adenosine monophosphate (cAMP) Porphobilinogen (PBG) Carcinoid syndrome is caused by a carcinoid tumor, which is a neuroendocrine tumor that is characterized by excessive production of serotonin and histamine. Carcinoid tumors are rare tumors that typically develop in the gastrointestinal tract. Carcinoid tumors are typically silent until hepatic metastasis occurs. Prior to metastasis, serotonin produced by the tumor undergoes first pass metabolism and is eliminated by the liver. Once hepatic metastasis occurs, the first pass metabolism is bypassed, the clinical manifestations develop. Clinical manifestations of carcinoid syndrome are multisystemic and include cardiac, pulmonary, GI, and cutaneous manifestations. Valvular involvement usually includes either tricuspid insufficiency or pulmonic stenosis (right-sided). Facial flushing observed in carcinoid syndrome is mediated primarily by vasodilatory actions of histamine, which is not affected by prostaglandin inhibition by aspirin. Pellagra (vitamin B3 deficiency) may occur when tryptophan is depleted by accelerated synthesis of serotonin, which is converted to 5-hydroxyindoleacetic acid (5-HIAA) and is excreted in the urine. Management of carcinoid syndrome is surgical resection, but pharmacologic therapy, such as octreotide, are usually administered to provide symptomatic relief.<br/> '''Educational Objective:''' Carcinoid syndrome is a neuroendocrine tumor that is characterized by excessive production of serotonin and histamine. Accelerated synthesis of serotonin by the carcinoid tumor is converted to 5-hydroxyindoleacetic acid (5-HIAA) and is excreted in the urine.<br/> '''References:''' Zuetenhorst JM, Taal BG. Metastatic carcinoid tumors: a clinical review. Oncologist. 2005;10(2):123-31.<br> First Aid 2015 page 336. Pathophysiology A 48-year-old woman with no past medical history presents to her physician's office with complaints of chronic watery diarrhea and occasional shortness of breath. She also complains of frequent abdominal pains that occasionally wake her up at night and intermittent facial flushing episodes which fail to respond to aspirin. Upon further questioning, she reports a 5 kg weight loss over the past 3 months and chronic fatigue. In the clinic, her blood pressure is 142/88 mmHg, heart rate is 90/min, and respiratory rate is 22/min. Cardiothoracic examination is remarkable for wheezing and a holosystolic murmur at the lower left sternal border that is intensified by applying pressure on her liver. Abdominal exam is remarkable for abdominal tenderness in the right lower quadrant, hyperactive bowel sounds, and mild hepatomegaly. Which of the following urinary findings are diagnostic of this patient's condition? B Oncology 2020-10-28T02:52:43Z 2459150.6199421 WBR245