Levothyroxin

Levothyroxin, or levothyroxine, is a synthetic form of the thyroid hormone thyroxine (T4). It is the standard replacement therapy for hypothyroidism, including autoimmune thyroiditis, after thyroidectomy, and following radioactive iodine treatment. It is also used to suppress TSH in certain thyroid cancers.

Levothyroxine is given as levothyroxine sodium. It is converted to the active hormone T3 in tissues and acts on nuclear receptors to regulate metabolism and development.

Taken orally once daily on an empty stomach with water, 30 to 60 minutes before breakfast (or as advised to maintain consistent timing). Dosing is individualized; typical initial doses range from 25 to 50 micrograms daily in healthy adults, with lower doses in older patients or those with cardiac disease. TSH levels are checked 4 to 6 weeks after starting or adjusting, then every 6 to 12 months when stable.

Monitor TSH and free T4; pregnancy increases thyroid hormone requirements. Adverse effects reflect excess thyroid hormone and may include palpitations, insomnia, and weight loss. Overdose risks include atrial fibrillation and osteoporosis with long-term use. Drug interactions can reduce absorption or alter metabolism, including calcium and iron preparations, aluminum-containing antacids, sucralfate, cholestyramine, and some proton pump inhibitors; rifampin and certain anticonvulsants can increase clearance; warfarin may require dose adjustments.

Available as generic levothyroxine tablets. Store at room temperature and take consistently with regard to meals and timing to maintain stable absorption. Dosage may need adjustment during pregnancy or changing health conditions.