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.

Hypothyroidism Causes

• Loss of thyroid tissue: Treatment of hyperthyroidism by radioactive destruction of thyroid tissue or surgical removal of thyroid tissue can result in hypothyroidism.
  
• Antithyroid antibodies: These may be present in people who have diabetes, lupus, rheumatoid arthritis, chronic hepatitis, or Sjogren's syndrome. These antibodies may cause decreased production of thyroid hormones.
  
• Congenital: Hypothyroidism can be present from birth. This is commonly discovered early with nationwide newborn screening for this disease.
  
• Defects in the production of thyroid hormone: Hashimoto's thyroiditis occurs when there are defects in the production of thyroid hormone, resulting in an increased amount of TSH. The increased TSH results in a goiter (enlargement of the thyroid gland itself that can be seen as an obvious swelling in the front of the neck).
  
• Medications: Some medications, particularly lithium (Eskalith, Lithobid), may cause a drug-induced hypothyroidism.