A Case of Non-islet Cell Tumor Hypoglycemia Secondary to Metastatic Rectal Adenocarcinoma: Presentation, Management, and Literature Review.

Background/Aim: Non-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome associated with a variety of benign and malignant tumors. It is most commonly associated with tumors of epithelial or mesenchymal origin. Management of NICTH primarily involves resection of the underlying tumor, along with other therapies. We report a case of NICTH secondary to metastatic rectal adenocarcinoma. While NICTH has previously been associated with colorectal cancers, few cases (if any) have been reported in patients with primary rectal cancer. Case Report: We present the case of a 51-year-old male with a medical history of pre-diabetes, gastroesophageal reflux disease, and tobacco use disorder. He was admitted for evaluation of rapid weight loss and was found to have rectal thickening, along with lesions in the lungs, liver, pancreas, and other sites, raising concern for metastasis. He underwent a colonoscopy with biopsy, which confirmed primary rectal adenocarcinoma. During his inpatient stay, he experienced recurrent episodes of hypoglycemia. A diagnosis of NICTH was supported by the low levels of pro-insulin, insulin, C-peptide, IGF-I and an elevated IGF-II:IGF-I ratio. The patient was treated with corticosteroids, glucagon, continuous dextrose infusions, and parenteral nutrition to manage hypoglycemia. Conclusion: This case highlights the importance of considering NICTH in the differential diagnosis for patients with unexplained or refractory hypoglycemia, especially when a notable mass or malignancy is suspected. It also highlights the need for a multimodal approach in managing the underlying hypoglycemia.