Levothyroxine is apparently the second most prescribed medication in the United States with 23.8 million prescriptions.

History: Levothyroxine was isolated in 1914 at the Mayo Clinic and then synthesized by British chemists in 1927.  

Brand names: Synthroid, Levothyroid, Levoxyl, Unithryoid

How it works:  Levothyroxine (T4) is a synthetic form of thyroxine, an endogenous hormone secreted by the thyroid gland. T4 is converted to its active metabolite, L-triiodothyronine (T3). Thyroid hormones (T4 and T3) then bind to thyroid receptor proteins in the cell nucleus and exert metabolic effects through control of DNA transcription and protein synthesis; involved in normal metabolism, growth, and development; promotes gluconeogenesis, increases utilization and mobilization of glycogen stores, and stimulates protein synthesis, increases basal metabolic rate (source: UptoDate)

Used for:  Hypothyrodism and pituitary thyrotropin-stiumulating hormone suppression

Cautions: Can cause heart palpitations, nausea, anxiousness, abdominal pain, weight loss, insomnia, increased appetite

Food interactions: Levothyroxine should be taken in the morning on an empty stomach thirty minutes before food.  Some foods interact with the binding of levothyroxine and can affect absorption (iron, calcium supplements).  

EducationJoanna Simmon