TY - JOUR T1 - 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? JF - BMJ Case Reports JO - BMJ Case Reports DO - 10.1136/bcr-2018-227430 VL - 12 IS - 3 SP - e227430 AU - Richard Fagan AU - Syed Sabeeh Najam Bokhari AU - Faisal Inayat Y1 - 2019/03/01 UR - http://casereports.bmj.com/content/12/3/e227430.abstract N2 - 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. ER -