(CSEMP056) LEVERAGING CONTINUOUS GLUCOSE MONITORS TO EXPEDITE THE MANAGEMENT OF HYPOGLYCEMIA DUE TO INSULINOMA

Abstract:

Background: Neuroendocrine tumors (NETs) are rare neoplasms with an estimated yearly incidence of 6 per 100 000 (Hallet et al., 2015), originating from various sites. Among pancreatic NETs, insulinomas represent the most common functioning subtype and are characterized by neoplastic endogenous hyperinsulinism. Patients with insulinoma often experience significant diagnostic delays (Basuroy et al., 2018) leading to prolonged exposure to hypoglycemia. Despite known diagnostic inaccuracies associated with continuous glucose monitors (CGMs) (Lindner et al., 2021), they are increasingly utilized to investigate nondiabetic hypoglycemia.

Case: A 62-year-old man was referred to our institution due to suspected insulinoma, based on recurrent symptomatic hypoglycemic episodes with a positive Whipple’s triad. His general practitioner provided him with a Freestyle Libre CGM, which revealed hypogylcemia 82% of the time (including 66% of severe hypoglycemic episodes < 3mmol/L) and normal glucose level 18% of the time over the span of a 4-day period (c.f. attached figures below). The patient had a past medical history significant only for benign prostatic hyperplasia (BPH) and hypertension. He had no history of diabetes, excessive alcohol use and was not on sulfonylureas on insulin therapy. He underwent a complete fasting challenge, which indicated hypoglycemia (2.4 mmol/L) at 3h, along with inappropriately normal insulin secretion (35.5 pmoL/L – reference range [13 ; 161] pmol/L), abnormally elevated C-peptide level (0.484 nmol/L – reference range [0.400 ; 1.470] nmol/L) and suppressed β-hydroxybutyrate levels ( < 0.1 mmol/L). Morning cortisol level was within normal limits (446 nmol/L). A CT scan of the abdomen and pelvis revealed a 1.8cm hypervascular lesion at the tail of the pancreas, consistent with a NET without evidence of distant metastases. Subsequently, the patient was admitted for treatment with intravenous dextrose and gradual uptitration of diazoxide to manage recurrent hypoglycemic episodes. He is presently awaiting surgical resection of the pancreatic mass.


Discussion: Hypoglycemia in non-diabetic patients is a rare condition that can manifest with discrete spells, often challenging to identify in an outpatient setting. Despite the inherent accuracy limitations, this case underscores the pivotal role of CGMs in diagnosing insulinoma and expediting referrals to specialized centers. Furthermore, CGMs may also facilitate identification of unrecognized hypoglycemic events in patients with prolonged hypoglycemia exposure (Unger & Parkin, 2011).