A 34-year-old man with generalized anxiety disorder has been taking propranolol 80 mg daily for 2 weeks with good symptom control. He discontinues the medication abruptly without medical guidance due to side effects. Within 48 hours, he presents to the emergency department with severe tremor, palpitations, and anxiety. Vital signs: BP 158/92 mmHg, HR 118 bpm, RR 20/min, temperature 37.2°C. Physical examination reveals bilateral fine tremor at rest and diaphoresis. EKG shows sinus tachycardia with normal ST segments. TSH level is normal. The patient denies chest pain, dyspnea, or recent illness. Which of the following best explains the pathophysiologic mechanism of his acute clinical deterioration?

1. A)Upregulation of beta-adrenergic receptors during chronic beta-blockade, leading to unopposed sympathomimetic effects upon drug withdrawalGABARITO
2. B)Acute depletion of central norepinephrine stores causing rebound CNS excitability and hyperventilation
3. C)Return of untreated baseline generalized anxiety disorder with physiologic manifestations of panic
4. D)Propranolol-induced suppression of thyroid hormone metabolism with subsequent thyrotoxicosis
5. E)Acute withdrawal syndrome characterized by decreased GABA and increased glutamate activity in the CNS