SAT-323 "Not Your Usual Suspect: Ovarian Tumor As A Source Of Recurrent Hypoglycemia"

Abstract Disclosure: C.A. Onuegbu: None. R. Lopez Fanas: None. M. Aziz: None. N. Suda: None. Background: Non-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome characterized by solid tumors secreting incompletely processed insulin-like growth factor-2 (IGF-2), exerting insulin-like effects. We report a rare case of malignant struma ovarii as the probable source of excess IGF-2, resulting in recurrent hypoglycemia. Case Presentation: A 68-year-old woman presented with abdominal discomfort, 60-pound unintentional weight loss and early satiety for a year. Imaging revealed a 9.8 cm right adnexal mass and a known benign pancreatic head intraductal papillary mucinous neoplasm. During her hospitalization, she experienced recurrent symptomatic fasting hypoglycemia, with serum glucose nadir of 59 mg/dL with symptoms of fatigue, lightheadedness, and dizziness consistent with level 2 hypoglycemia. Her symptoms resolved after administration of intravenous (IV) dextrose. She had a prior admission with stroke-like symptoms and a serum glucose of 51 mg/dL, with resolution of symptoms after IV dextrose. She had no history of bariatric surgery and was not taking hypoglycemic agents. Laboratory tests revealed: glucose 63 mg/dL, insulin <3 μIU/mL, C-peptide 1.49 ng/mL (0.81-3.85), HbA1c 4.2%, random cortisol 19.3 μg/dL (4-20), albumin 1.9 g/dL (3.5-5), TSH 1.05 μU/mL (0.3-4.2), IGF-2 320 ng/mL (267-616), IGF-1 16 ng/mL (34-194), IGF-2:IGF-1 ratio of 20, IGF-binding protein-2 (IGFBP-2) 333 ng/mL (47-350). Liver and kidney function were normal. She underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy. The pathology revealed malignant struma ovarii with stromal carcinoid component demonstrating thyroid and neuroendocrine features. Immunohistochemistry was positive for neuroendocrine markers chromogranin and synaptophysin, and calretinin (a marker for mesothelioma). Postoperatively, her blood glucose levels normalized, ranging from 77-126 mg/dL. Unfortunately, she died from septic shock secondary to aspiration pneumonia. Discussion: NICTH presents with fasting hypoglycemia and suppressed insulin levels, typically due to tumor overproduction of IGF-2. IGF-2 increases glucose uptake via insulin receptor activation and impairs counter-regulatory hormones glucagon and growth hormone. Diagnosis can be made despite normal IGF-2 levels, as normal IGFBP-2 with hypoalbuminemia suggests elevated free IGF-2. Struma ovarii is a rare ovarian tumor containing thyroid tissue; the presence of carcinoid features is even rarer and may confer more aggressive behavior. To our knowledge, struma ovarii has not been previously reported as a source of IGF-2. Although IGF-2 staining was unavailable, resolution of hypoglycemia post-resection, and an IGF ratio of 20 implicates the tumor as the source. Surgery is curative, though corticosteroids, growth hormone, or somatostatin analogues are utilized when surgery is not feasible. Presentation: Saturday, July 12, 2025