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Vitamin D and vitamin B12 deficiencies in patients with small intestinal carcinoid tumour: is opioid use disorder a confounding factor in the diagnosis?
  1. Richard Fagan1,
  2. Syed Sabeeh Najam Bokhari1 and
  3. Faisal Inayat2
  1. 1 West Suburban Medical Center, Oak Park, Illinois, USA
  2. 2 Allama Iqbal Medical College, Lahore, Pakistan
  1. Correspondence to Dr Faisal Inayat, faisalinayat{at}


Carcinoid tumours have the ability to secrete various peptides and bioamines that lead to carcinoid syndrome manifested as cutaneous flushing, diarrhoea, bronchial constriction and cardiac involvement. The deficiencies of vitamins D and B12 have previously been reported in patients with carcinoid tumours presumably due to chronic diarrhoea associated with the carcinoid syndrome. Herein, we chronicle the case of a patient with opioid use disorder who presented with small bowel obstruction that was found to be caused by a midgut carcinoid tumour. Laboratory studies revealed deficiencies of vitamins D and B12 even though he denied diarrhoea and had no other aetiology of deficiencies of these vitamins. Additionally, this paper presents a review of the published medical literature pertaining to clinical features, diagnostic investigations and treatment of intestinal carcinoid tumours and explores possible explanations for the observed deficiencies in these patients.

  • gastroenterology
  • small intestine cancer
  • malabsorption
  • vitamins and supplements
  • general practice / family medicine

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  • Contributors RF: designed the study, drafted, reviewed, and revised the manuscript. SSNB: contributed to the case presentation, reviewed the manuscript, and suggested pertinent modifications. FI: performed the literature review, drafted and revised the manuscript critically for important intellectual content, and gave the final approval for the version published.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Not required.