Case Presentation: A previously healthy 17-year-old girl was brought to the emergency department (ED) by ambulance following a generalized tonic-clonic seizure. Her blood glucose was 61 mg/dL at the scene and 31 mg/dL on arrival to the ED. A basic metabolic panel was obtained and was within normal limits with the exception of low plasma glucose at 30 mg/dL. She was given a dextrose bolus and transferred to our facility. She reported she had felt normal prior to the seizure, she had been fasting for approximately 12 hours (overnight) but this was not unusual for her. She denied headache, dizziness, lightheadedness, or weakness. She denied taking any medications, alcohol, or drugs of abuse. Her pet dog has insulin dependent diabetes, but she denied coming in contact with her dog’s insulin within the preceding two days. Upon admission, she was started on dextrose containing intravenous (IV) fluids. Her history is only significant for late menarche at age 16 and maternal family history includes adrenal insufficiency, Crohn’s disease, and lupus. She was admitted to our hospital for evaluation of hypoglycemia.
Discussion: During her admission, IV fluids were weaned off and she was started on a fast. Within 6 hours she became hypoglycemic to 44 mg/dL. Critical labs were obtained revealing normal serum electrolytes, serum beta-hydroxybutyrate levels, growth hormone, and cortisol. Insulin level at this time was 14.0 u/mL and C-peptide was 2.05 ng/mL. A glucagon stimulation test was performed and she responded with a rise in blood glucose to 71 mg/dL. Overall, non-ketotic hypoglycemia with positive glucagon stimulation test and elevated insulin level was concerning for endogenous hyperinsulinemia. She did not have any further seizure activity and remained at her neurologic baseline throughout admission. She was transferred to an adult hospital where she underwent PET CT and endoscopic ultrasound with fine needle aspiration of the pancreas, neither of which identified an insulinoma. She was started on diazoxide and discharged with outpatient endocrinology follow-up. She will be undergoing genetic testing in the near future.
Conclusions: Non-ketotic, non-acidotic hypoglycemia suggests a narrow differential: endogenous or exogenous hyperinsulinemia or a defect in fatty acid metabolism. Our patient’s history and labs were not consistent with exogenous insulin, beta-blockers, or other exogenous agents. Her lack of symptoms in childhood and later her reassuring fatty acid studies, argued against a metabolic disorder. Through timely, systematic laboratory evaluation we were able to identify endogenous hyperinsulinemia as her cause. Insulinomas are a rare cause of pediatric hypoglycemia, however must be considered when children have recurrent or persistent hypoglycemia. The next step in insulinoma evaluation is imaging for surgical planning. Genetic testing (ie. MEN1) should be considered, especially in children, as pediatric cases are more strongly associated with MEN1 than adults. Our patient was asymptomatic until the seizure, likely indicating that she was acclimated to being in a hypoglycemic state and felt normal until her blood glucose was critically low. In this case, pinpointing the non-ketotic, non-acidotic hypoglycemia and performing a thorough, methodical endocrine evaluation were key in establishing a diagnosis for our patient.