Adverse Effects of Treatment With Thyroid Hormone

ADVERSE EFFECTS OF TREATMENT WITH THYROID HORMONE

The most common adverse effects (i.e., symptoms of hy-perthyroidism) are the result of a drug overdose; they include cardiac palpitation and arrhythmias, tachycar-dia, weight loss, tremor, headache, insomnia, and heat intolerance. Symptoms subside if medication is withheld for several days.

In patients with longstanding hypothyroidism and those with ischemic heart disease, rapid correction of hypothyroidism may precipitate angina, cardiac ar-rhythmias, or other adverse effects. For these patients, replacement therapy should be started at low initial doses, followed by slow titration to full replacement as tolerated over several months. If hypothyroidism and some degree of adrenal insufficiency coexist, an appro-priate adjustment of the corticosteroid replacement must be initiated prior to thyroid hormone replacement therapy. This prevents acute adrenocortical insufficiency that could otherwise arise from a thyroid hormone– induced increase in the metabolic clearance rate of adrenocortical hormones.