A 41-year-old male presents with polydipsia, polyphagia, and rapid weight loss for over 2 months (BMI 21). After consuming contaminated food, he developed nausea, vomiting, and somnolence for 1 day. Examination reveals confusion, dehydration, fruity breath odor, heart rate 127 bpm, BP 80/56 mmHg, grade I thyroid enlargement (no vascular bruit), and bilateral exophthalmos (16 mm). Lab results: blood glucose 26.8 mmol/L, urine ketones (++++). Which primary condition is most likely?