MON-313 - A Rare Cause of Hypoglycemia

Background: Non–islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome most commonly associated with solitary fibrous tumors (SFTs). Hypoglycemia is mediated by tumor-derived insulin-like growth factor-2 (IGF-2), known as Doege–Potter syndrome. Diagnosis is often delayed due to nonspecific symptoms and misleading laboratory findings.

Case Presentation: A 58-year-old woman with no known medical history presented with nine months of progressive abdominal bloating, early satiety, anorexia, and food intolerance, resulting in a 50-pound unintentional weight loss. She also reported intermittent adrenergic and neuroglycopenic symptoms relieved by eating. She was admitted after being found unresponsive at home with severe hypoglycemia (plasma glucose 18 mg/dL).

Computed tomography of the abdomen revealed a large central abdominal mass arising from the mesentery with mass effect on adjacent structures. During hypoglycemia (plasma glucose 58 mg/dL), laboratory evaluation demonstrated undetectable insulin and C-peptide levels with suppressed beta-hydroxybutyrate. Insulin-like growth factor-1 (IGF-1) was markedly reduced at 14 ng/mL (reference range 41–279 ng/mL), while IGF-2 measured within the laboratory reference range at 332 ng/mL. This represented a key diagnostic pitfall, as standard immunoassays may not reliably detect high-molecular-weight “big” IGF-2 preferentially secreted by these tumors. A comprehensive hypoglycemia evaluation was otherwise unremarkable, with no exposure to exogenous insulin or insulin secretagogues. Biopsy confirmed a solitary fibrous tumor.

The patient developed persistent hypoglycemia requiring continuous intravenous dextrose. Glycemic control improved with glucocorticoid therapy, and total parenteral nutrition provided additional stabilization. She subsequently underwent complete surgical resection of the tumor. Following tumor removal, hypoglycemia resolved completely, and glucocorticoids were discontinued without recurrence.

Discussion: NICTH should be suspected in patients with recurrent hypoglycemia, suppressed insulin markers, low IGF-1, and large mesenchymal tumors. Excess IGF-2 promotes hypoglycemia through increased peripheral glucose uptake and suppression of counterregulatory hormones. Normal total IGF-2 levels do not exclude the diagnosis and represent an important diagnostic pitfall.

Clinical Implication: Low IGF-1 with suppressed insulin and C-peptide in the setting of a large tumor should prompt consideration of NICTH, even when IGF-2 levels are within the reference range.

Conclusion: Doege–Potter syndrome is a rare but life-threatening cause of hypoglycemia. Surgical resection is definitive therapy, while glucocorticoids and nutritional support are effective temporizing measures

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