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Tuesday, 4 December 2012

Thyroxine replacement in ischaemic heart disease

Hypothyroidism and ischaemic heart disease are both common, so inevitably they will sometimes occur together. Although angina may remain unchanged in severity or paradoxically disappear with restoration of metabolic rate, exacerbation of myocardial ischaemia, infarction and sudden death are well-recognised complications of thyroxine replacement, even using doses as low as 25 μg per day. In patients with known ischaemic heart disease, thyroxine should be introduced at low dose and increased very slowly under specialist supervision. It has been suggested that T3 has an advantage over T4, since T3 has a shorter half-life and any adverse effect will reverse more quickly, but the more distinct peak in hormone levels after each dose of T3 is a disadvantage. Approximately 40% of patients with angina cannot tolerate full replacement therapy despite the use of β-blockers and vasodilators; coronary artery surgery or balloon angioplasty can be performed safely in such patients and, if successful, allow full replacement dosage of thyroxine in the majority