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Carcinoid syndrome — SCE Endocrinology MCQ

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HardMEN/NET/MiscellaneousCarcinoid syndromeSCE Endocrinology

A patient with metastatic midgut neuroendocrine tumour has persistent six-times-daily secretory diarrhoea and raised 5-HIAA despite optimised long-acting octreotide. Imaging shows stable tumour burden and infection has been excluded. What addition most specifically targets serotonin-mediated diarrhoea?

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Correct answer: A — Telotristat added to ongoing somatostatin-analogue therapy

The best answer is “Telotristat added to ongoing somatostatin-analogue therapy”. Telotristat inhibits tryptophan hydroxylase and reduces peripheral serotonin production, making it an evidence-based add-on for refractory carcinoid-syndrome diarrhoea despite a somatostatin analogue. “Stop the somatostatin analogue and use loperamide alone” is less appropriate because supportive antidiarrhoeal treatment does not replace tumour- and serotonin-directed therapy “Start carbimazole to reduce serotonin synthesis” is less appropriate because carbimazole inhibits thyroid hormone synthesis and has no effect on serotonin “Give high-dose levothyroxine to slow intestinal transit” is less appropriate because thyroid hormone can accelerate rather than slow gut transit and does not treat the syndrome “Use hydrocortisone as lifelong monotherapy” is less appropriate because glucocorticoid replacement has no specific role in serotonin-mediated diarrhoea

Reference: ENETS guidance paper for carcinoid syndrome. https://pmc.ncbi.nlm.nih.gov/articles/PMC9539661/