{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,28]],"date-time":"2025-08-28T12:43:26Z","timestamp":1756385006677,"version":"3.44.0"},"reference-count":31,"publisher":"BMJ","issue":"3","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2019,2,23]]},"published-print":{"date-parts":[[2019,3]]},"abstract":"<jats:p>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 B<jats:sub>12<\/jats:sub> 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 B<jats:sub>12<\/jats:sub> 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.<\/jats:p>","DOI":"10.1136\/bcr-2018-227430","type":"journal-article","created":{"date-parts":[[2019,3,16]],"date-time":"2019-03-16T14:45:11Z","timestamp":1552747511000},"page":"e227430","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":3,"title":["Vitamin D and vitamin B<sub>12<\/sub> deficiencies in patients with small intestinal carcinoid tumour: is opioid use disorder a confounding factor in the diagnosis?"],"prefix":"10.1136","volume":"12","author":[{"given":"Richard","family":"Fagan","sequence":"first","affiliation":[{"name":"West Suburban Medical Center, Oak Park, Illinois, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Syed Sabeeh Najam","family":"Bokhari","sequence":"additional","affiliation":[{"name":"West Suburban Medical Center, Oak Park, Illinois, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7576-7319","authenticated-orcid":false,"given":"Faisal","family":"Inayat","sequence":"additional","affiliation":[{"name":"Allama Iqbal Medical College, Lahore, Pakistan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2019,3,16]]},"reference":[{"key":"2025082703181826000_12.3.e227430.1","doi-asserted-by":"publisher","DOI":"10.1097\/00001503-200306000-00017"},{"key":"2025082703181826000_12.3.e227430.2","doi-asserted-by":"publisher","DOI":"10.1093\/ageing\/afr122"},{"key":"2025082703181826000_12.3.e227430.3","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.hoc.2015.09.001","article-title":"Surgical treatment of small bowel neuroendocrine tumors","volume":"30","author":"Farley","year":"2016","journal-title":"Hematol Oncol Clin North Am"},{"key":"2025082703181826000_12.3.e227430.4","doi-asserted-by":"crossref","DOI":"10.1186\/1477-7819-4-35","article-title":"Liver metastases of neuroendocrine tumours; early reduction of tumour load to improve life expectancy","volume":"4","author":"Veenendaal","year":"2006","journal-title":"World J Surg Oncol"},{"key":"2025082703181826000_12.3.e227430.5","doi-asserted-by":"publisher","DOI":"10.1016\/j.humpath.2004.09.018"},{"key":"2025082703181826000_12.3.e227430.6","doi-asserted-by":"publisher","DOI":"10.1159\/000335629"},{"key":"2025082703181826000_12.3.e227430.7","first-page":"720","article-title":"Mesenteric angiopathy, intestinal gangrene, and midgut carcinoids","volume":"90","author":"Eckhauser","year":"1981","journal-title":"Surgery"},{"key":"2025082703181826000_12.3.e227430.8","doi-asserted-by":"publisher","DOI":"10.1093\/ajcp\/56.4.452"},{"key":"2025082703181826000_12.3.e227430.9","doi-asserted-by":"publisher","DOI":"10.1016\/j.beem.2004.10.003"},{"key":"2025082703181826000_12.3.e227430.10","doi-asserted-by":"publisher","DOI":"10.1097\/00007611-198912000-00011"},{"key":"2025082703181826000_12.3.e227430.11","doi-asserted-by":"publisher","DOI":"10.2165\/00003495-200363070-00003"},{"key":"2025082703181826000_12.3.e227430.12","unstructured":"Chew JM , Hui EK . 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