Hypothyroidism Medications

• L-thyroxine (Synthroid, Levoxyl, Levothroid, Unithroid): This medication is the mainstay of thyroid hormone replacement therapy in hypothyroidism. This is a synthetic form of thyroxine. This is exactly the same hormone that the thyroid makes. The body tissues convert it to the active product L-triiodothyronine. Side effects are rare, and it has an excellent safety record.

• L-triiodothyronine: This is rarely used alone as thyroid hormone replacement, because it has a much shorter persistence in the blood than L-thyroxine. Its use can cause rapid increases in L-triiodothyronine concentration, which can be dangerous in the elderly and in people with cardiac disease. It may be used in combination with L-thyroxine for people who have poor symptomatic relief with L-thyroxine alone.
  
  
• Thyroid extract or "natural" thyroid hormone: This is dried and powdered pig thyroid gland. The hormone is not purified and the exact amount of T4 and T3 can be variable. This is not recommended as a thyroid hormone replacement. There is an excess of T3 in this preparation.