SAT150 "Sawtooth" Hypoglycemia: Rare Case Of IGF-2 Mediated Hypoglycemia With Elevated Proinsulin Level And "Sawtooth" Pattern On CGMS

Abstract

Abstract Disclosure: P. Goparaju: None. M. Zena: None. Background: IGF-2 mediated hypoglycemia is usually associated with low Insulin, C-peptide and Proinsulin levels. We present an extremely rare case of IGF-2 mediated hypoglycemia with elevated Proinsulin level and an unusual “saw tooth” pattern on Continuous glucose monitoring system(CGMS). Clinical Case: 53-year-old male with history of metastatic Liposarcoma was admitted to the hospital with severe hypoglycemia. Whipple’s triad was positive on presentation, patient had symptoms of altered sensorium, blood glucose of 24 mg/dl, and symptoms improved upon correction of hypoglycemia. The patient was admitted to the ICU and IV dextrose was initiated.As Liposarcomas are known to be associated with Non-islet cell tumor hypoglycemia (NICTH), treatment with Prednisone was started. Prior to this, initial hypoglycemia workup was sent when blood sample was drawn during a hypoglycemia episode. Patient has no personal or family history of Diabetes. Adrenal insufficiency was ruled out with morning cortisol of 17.8 ug/dl. Serum glucose was low at 40mg/dl, Insulin<1(0-17 pmol/L), C-peptide level low at 0.4 (0.8-3.9 ng/ml), IGF-1 level was low at 68 (74-225 ng/ml), normal IGF-2 at 626 (333-967 ng/ml) and increased IGF-2/IGF-1 ratio of 9.2(Normally around 3:1). All the lab work above is consistent with IGF-2 mediated hypoglycemia with low Insulin, C-peptide and IGF-1 levels and increased IGF-2/IGF-1 ratio. Interestingly, he has an elevated Proinsulin level of 36.9 (0.0-10.0 pmol/L) which is very unusual.Prednisone was started at 20mg daily to which there was reasonable response, dose was eventually increased to 60mg daily before he was safely sent home. He was discharged on a CGMS and the data was downloaded 2 weeks later. He had an interesting “Saw tooth” pattern of glycemia on the daily glucose graphs. As the patient had access to live data, he was trying to correct the falling blood glucose which briefly improved the readings but was quickly followed by another drop and this sequence carried on leading to a unique blood glucose pattern on the CGMS. Conclusion: Proinsulin level is usually suppressed in IGF-2 mediated hypoglycemia. Our case is unusually associated with high Proinsulin level. One hypothesis is the possible structural similarities leading to lab assay interactions between Proinsulin and “Pro-IGF-2”, which is thought to be one of the main molecules responsible for hypoglycemia in this condition. More studies in future will be helpful to study this possible association. Our case also had a remarkable “Saw tooth” pattern on CGMS glucose graphs which is very rarely seen in clinical practice.