I have been taking Synthroid for many years. A March report in the From the Pharmacy column indicates that this drug contains T4 thyroid hormone but not T3 hormone. Does that mean I am only getting half of what I need? It’s scary to think I’ve been shorting my system for so many years.
St. Augustine, Florida
Rest easy. Your body is able to turn the prescription drug Synthroid into the T3 hormone that you need.
A healthy thyroid gland produces the right amount of T3 (triiodothyronine) and T4 (thyroxine or tetraiodothyronine) to control the body’s rate of energy use. Doctors prescribe a synthetic version of T4 called levothyroxine (Synthroid, Levoxyl) when the gland is underactive or removed because of thyroid cancer or Graves’ disease, the most common cause of hyperthyroidism in the United States.
“The body converts, or makes, T3 from T4,” explains Dr. Jeffrey Garber, chief of endocrinology at Harvard Vanguard Medical Associates. “In fact, a 2008 study from Georgetown University Medical Center in Washington, D.C., reports normal T3 levels in those taking levothyroxine therapy.”