I. The plasma half-life of thyroxine is 1 day. II. Patients with hypothyroidism and hypertension or cardiovascular problems should begin levothyroxine therapy with a low dosage (12,5-25 mg).
Extra info: The thyroxine half-life is 8 days. Over 99% of the thyroxine binds to the plasma thyroglobulin. This explains the relatively long half-life of thyroxine. Levothyroxine therapy increases the risk of angina, arrhythmias, and myocardial infarction in patients that suffer from cardiovascular insufficiency. Therefore, thyroxine therapy should be given in low doses in these patients.