By Gary Pepper, M.D.
According to experts, 10 to 20% of hypothyroid individuals fail to respond completely to T4-only (levothyroxine, Synthroid) treatment. Dr. Anthony Bianco, the president of the American Thyroid Association, and his associates believe this is due to genetic variations in the way thyroid hormone is converted in the body from T4 into T3. T3 is the much more potent form of thyroid hormone and unless the cells of the body receive enough T3, normal function cannot be achieved and symptoms of low thyroid such as fatigue, mental fogginess, constipation, muscle aches etc, persist. Based on the research conducted by Dr. Bianco and colleagues it is thought that in those with the genetic trait making T4 treatment ineffective, blood tests would show low T3 levels. Continue reading