Subjects will undergo memory testing, a disease specific symptom questionnaire, a general mental health assessment, a complete physical examination, baseline EKG, and biochemical testing consisting of serum TSH, free T4, total T4, total T3, free T3, T3 resin uptake, reverse T3, sex hormone binding globulin (SHBG), serum iodine, a lipid panel, insulin, glucose and leptin. This testing and DXA scan of body composition will be performed at baseline and after each 3 month treatment period. Deiodinase type 2 (DIO2) polymorphisms analyses - will also be performed at the beginning of the study and the results will be blinded to the investigators performing the memory testing.