Q. An 8-year old boy presents to his pediatrician with complaints of increased thirst and urinary frequency over the past two months. He reports drinking more water than normal, along with frequent urination at night. Furthermore, he feels more tired than normal. The patient's vital signs at presentation are: BP 110/70 mmHg, HR 80 bpm and RR 16 bpm. A physical exam revealed no notable findings. Further testing revealed a plasma glucose of 210 mg/dl. The patient is given insulin therapy and instructed to follow a diabetic diet. For further care, they are referred to a pediatric endocrinologist. What is the pathophysiology of this disease?