Our hypothesis is that hypothyroid patients on DTE may have a decrease in symptoms, an improvement of cognitive function, and an increase in sense of well-being/ quality of life equivalently compared with L-T4.

Inclusion Criteria:

• Patients will be between the ages of 18 to 65 and will have been on levothyroxine for primary hypothyroidism for at least 6 months.

Exclusion Criteria:

• Patients will be excluded if they have the following problems: pregnancy, plan for pregnancy in the next 12 months, cardiac disease, especially coronary artery disease, chronic obstructive lung disease, malabsorption disorder, gastrointestinal surgeries, significant renal or liver dysfunction, seizure disorders, thyroid and non-thyroid active cancers, uncontrolled psychosis, psychotropic medication use, steroid use, amiodarone, chemotherapy for cancer, iron supplement more than 325mg per day, carafate/ proton pump inhibitor use, cholestyramine use, and those with recent PCS orders who are expected to move out of the geographic area, age less than 18 years old or older than 65 years old.
• Patients scheduled for deployment will be excluded.