MON-145 An Unusual Cause of Hypoglycemia in a Non-Diabetic Elderly Male

Introduction: Hypoglycemia (HYPO) in non-diabetic patients is an unusual scenario and presents a diagnostic challenge, resulting in serious consequences for patients. We describe the case of an elderly non-diabetic male who developed severe persistent HYPO. Case: A 78-year-old male with history of macroprolactinoma taking bromocriptine, Hashimoto's hypothyroidism, initially treated with low dose L-thyroxine, followed by Graves' hyperthyroidism, Parkinson’s disease (PD), osteopenia was noted to have hypoglycemia (54 mg/dL) on routine lab work. When questioned, he admitted to having had years of lightheaded episodes, "feeling jittery", which improved within minutes after eating sugary foods. His wife mentioned that he “loved to eat sweets” and high simple carbohydrate meals(CARBS). Physical exam - orthostatic hypotension and mild resting tremors, both attributed to PD. Continuous glucose monitoring (CGMS) was performed for 2 weeks which documented HYPO overnight while sleeping, fasting and between meals. The HYPO was associated more frequently with sweet bedtime snacks. Laboratory- Glucose tolerance test was stopped due to HYPO with symptoms. ACTH=19 pg/mL (nl 0-47), AM Cortisol 19.4 microg/dL (nl 5.3-22.5), fasting blood glucose 83 mg/dL(nl 70-99), fasting insulin 6.9 mIU/L( nl 0-24.9), proinsulin 16.9 pmol/L ( nl <=18.8 pmol/L), c-peptide 1.39 ng/mL( nl 0.81-3.85), beta-OH butyrate 0.072 mmol/L( nl 0.020-0.270). Islet cell Ab was normal. Gastric emptying study was negative. Although the dose of bromocriptine was reduced due to HYPO, it continued. He was advised to decrease intake of CARBS, eat small, high protein and fat meals with frequent snacks. On subsequent visits, he reported less hypoglycemic episodes with improved energy level and general well-being, which was confirmed by CGMS. Discussion: Although a wide range of diseases can cause HYPO in nondiabetic patients, differences in characteristics between non-diabetic HYPO and diabetic HYPO have not been well studied. Common underlying diseases associated with HYPO include malignancies, cerebrovascular diseases, infection, major organ failure, and alcohol-related disorders. In addition, comorbidities linked with HYPO include sepsis, kidney diseases, and alcohol dependence, pneumonia, liver diseases and insulin abuse. Malnutrition, alcohol, infection, and post gastrectomy are the leading causes of nondiabetic hypoglycemia. In addition, methimazole use has been associated with insulin autoimmune syndrome resulting in HYPO due to interaction of sulfhydryl group with disulfide bond in the insulin molecule Conclusion: Clinicians should be aware of the potential for hypoglycemia in non-diabetic patients, due to other etiologies, which can also result in severe and possibly life-threatening sequelae. An in-depth evaluation, including the use of CGMS can assist in determining underlying causes.