A patient with hypothyroidism has been started on levothyroxine (Synthroid) therapy. The nurse is monitoring the patient for cardiovascular effects of the medication. Which finding would best explain why levothyroxine must be started at a low dose and gradually increased in patients with pre-existing heart conditions?
- Levothyroxine directly suppresses TSH, which reduces cardiac contractility
- Levothyroxine causes bradycardia and reduced cardiac output at therapeutic doses
- Levothyroxine enhances catecholamine sensitivity, which can increase myocardial oxygen demand and risk of MI
- Levothyroxine causes fluid retention, leading to acute decompensated heart failure