A 62-year-old man with newly diagnosed hypothyroidism started levothyroxine 50 mcg daily. Six weeks later, he presents with palpitations and irregular heartbeat. Vital signs show HR 118 bpm, BP 148/92 mmHg, RR 18, temperature 37.2°C, SpO2 98% on room air. ECG confirms atrial fibrillation. Labs reveal TSH 0.05 mIU/L (normal 0.4–4.0) and free T4 18 pg/dL (normal 7–20). Thyroid ultrasound shows no nodules. Which mechanism best explains his arrhythmia?
- A)Direct cardiotoxic effect of levothyroxine metabolites
- B)Levothyroxine dose is too high, causing iatrogenic thyrotoxicosisGABARITO
- C)Reactivation of Graves disease in response to levothyroxine
- D)Acute myocarditis triggered by levothyroxine
- E)Underlying cardiac arrhythmia unrelated to thyroid therapy
Explicação
This patient was over-replaced with levothyroxine, resulting in suppressed TSH (0.05) and elevated free T4 (18), creating an iatrogenic hyperthyroid state. Excess thyroid hormone increases cardiac oxygen demand, heart rate, and automaticity, increasing atrial ... Ver explicação completa e trilha adaptativa →