8094 When Low Blood Sugar Isn't Just A Lab Glitch
Authors: Kurt Merve , McLaughlin Christine D , Clancy Thomas E , Patti Mary-Elizabeth 
Published: October 2024

Abstract
Disclosure: M. Kurt: None. C.D. McLaughlin: None. T.E. Clancy: None. M. Patti: Advisory Board Member; Self; Fractyl Laboratories. Consulting Fee; Self; AstraZeneca, Hanmi Pharmaceuticals, MBX. Grant Recipient; Self; Dexcom.
Background: The diagnosis of hypoglycemia can be complex due to nonspecific symptoms, unawareness, and the variety of medical conditions which can contribute. Moreover, diagnosis can be confounded by artifactual factors, or so-called “pseudohypoglycemia.” Glucose consumption ex vivo may lead to falsely low glucose, especially in the setting of high white blood count as with leukemia. Here, we present a patient with chronic lymphocytic leukemia (CLL), whose initial diagnosis of artifactual hypoglycemia obscured the presence of an underlying insulinoma. Clinical Case: A 62-year-old male with a 13-year history of CLL, ITP, splenomegaly, and heart block was referred to an endocrinology clinic after his new PCP noted multiple low blood glucose readings ranging from 40-50 mg/dL over the past 10 years. These values were initially attributed to artifactual hypoglycemia in the context of his CLL (WBC 25-30,000/μL) and the absence of symptoms. However, upon detailed questioning, patient’s wife reported subtle jitteriness and mood changes when patient was hungry, which would subside rapidly upon eating. Patient denied any history of weight change, confusion, loss of consciousness, or seizure. Family history for multiple endocrine neoplasia (MEN) or hypoglycemia was negative. Laboratory testing revealed fasting blood glucose of 51 mg/dL, insulin 18.2 uIU/mL (≤19.6), proinsulin 55.5 pmol/L (≤18.8), C-peptide 3.78 ng/mL (0.8-3.85), and beta-hydroxybutyrate 0.05 mmol/L. Additional testing included negative sulfonylurea screen, negative insulin autoantibodies, normal IGF-2, and normal AM cortisol. Continuous glucose monitoring indicated that sensor glucose was &lt;70 mg/dL 46% of the time in both fasting and postprandial states. CT revealed a 1.8 cm well-circumscribed enhancing nodule in the tail of the pancreas. MRI suggested the lesion was accessory spleen, and DOTATATE scan was negative. Endoscopic ultrasound was inconclusive. Given the inconclusive imaging and the patient's high risk for blind exploratory surgery, a selective arterial calcium-stimulation test was performed. While arteriogram was negative, insulin secretion was stimulated by injection of calcium into the distal splenic artery, suggesting an insulinoma in the tail of the pancreas. Patient underwent distal pancreatectomy and splenectomy, and pathology confirmed an insulinoma. Postoperatively, hypoglycemia resolved. Genetic testing for MEN was negative. Discussion: Artifactual hypoglycemia is a phenomenon of erroneously low blood glucose measurements, particularly in patients with leukemia, where leukocytes consume glucose within the test tube. Despite these confounding factors, a thorough diagnostic investigation remains essential. This case highlights the importance of considering alternative diagnoses, even in asymptomatic patients with conditions known to cause artifactual hypoglycemia.
Presentation: 6/1/2024