Adult Onset Of Type 1 Diabetes Mellitus Preceded By Elevated Postprandial And Fasting Blood Glucose

HISTORY A 27 year old male reported polydipsia and polyuria for >3 weeks with concurrent weight loss despite caloric surplus of 500 kcal/day (weighed food logs and Fitbit Charge 2 HR (Fitbit Inc, San Francisco, CA, USA)). He reported 24-hour urinary output of 4 L. In prior 4 years, oral glucose tolerance and mixed meal tests revealed peak glucose over 200 mg/dl (204 - 247 mg/dL) and elevated fasting glucose (FG) (101 - 154 mg/dL) with normal HbA1c (4.9 - 5.4%). (Figure 1A) His sibling was diagnosed with type 1 diabetes (T1DM) at 9 years old leading to subjects participation in diabetes prevention trial at 7 years old which utilized oral insulin. He suspected some form of diabetes and requested further testing PHYSICAL EXAMINATION: Self-reports high levels of physical activity (weight lifting and running 6-7x per week) and follows plant-based diet with 3250 kcal / day (20% protein, 50% CHO, 30% fat). Weight, fat mass, and lean body mass were measured at home using an Aria 2 (Fitbit Inc, San Francisco, CA, USA) bioelectrical impedance scale. (Figure 1B) DIFFERENTIAL DIAGNOSIS: 1. T1DM 2. T2DM TEST AND RESULTS: Lab work revealed FG of 268 mg/dL and HbA1c of 9.8%. GAD antibody was elevated (9 IU/mL). Other measures were normal: ADH (2.2 pg/mL), BUN (17 mg/dL), creatinine ( 0.94 mg/dL), GFR (111 ml/min/BSA), urine osmolality (1,198 mOsm/kg) FINAL WORKING DIAGNOSIS: T1DM TREATMENT AND OUTCOMES: 1. Subject started insulin therapy with 20:1 carb to insulin ratio and began gaining weight concurrent with caloric surplus. 2. Weight 76.4 kg with a BMI of 22.7 kg/m2 after 11 weeks of initiating insulin. 3. From September 10th to 25th, honeymoon phase occurred and insulin needs dropped to 0 units/day. Several instances of hypoglycemia occurred with blood glucose values as low as 41 mg/dL 4. After honeymoon phase, daily insulin needs stabilized to 15 units basal and 20 units bolus suggesting partial endogenous insulin production