 Prior to and after surgery, the investigators will measure each patients thyroid levels TSH, free T4, total T4, total T3, thyroxine binding globulin, sex hormone binding globulin, lipid panel, and iron, and parathyroidcalcium function parathyroid hormone, calcium, albumin, vitamin D25, and deiodinase type 2 polymorphism status will be determined on pre-surgery bloodwork. Thyronamine levels will also be measured before and after surgery. Thyronamines are thyronergic metabolites of thyroid hormones that can decrease metabolism and induce behavioral inactivity in mouse models. A recently developed sensitive chemiluminescent antibody assay for 3-Iodothyronamine has been developed and patients on levothyroxine therapy after thyroidectomy had higher thyronamine levels compared with euthyroid controls. Based on these studies, the investigators hypothesize, as a secondary measure that patients with a higher thyronamine level after surgery, or greater pre- vs post-surgery thyronamine level will have worse outcomes, defined by the questionnaires. Patients will complete a series of questionnaires SF-36 measure of overall health, Billewicz measure of thyroid health, HADS measure of anxiety and depression as well as undergo working memory testing using the N-back and cognitive function testing using the Sustained Attention to Response Test SART. Lab analysis will also be performed before surgery to look at targets of thyroid hormone action including low density lipoprotein LDL cholesterol and sex hormone binding globulin SHBG. Following surgery, only patients who do not have evidence of thyroid cancer or patients with incidental, clinically indolent thyroid cancer not requiring radioiodine therapy or TSH suppression will continue on the study. The patients continuing in the study will have their dose of levothyroxine titrated with the goal of matching their pre-surgery TSH - 1 milli-international units per liter mIUL. 6 months following surgery, lab testing, questionnaires and cognitive testing will be repeated. Timing the second set of testing 6 months will allow adequate time to match the post-surgery TSH to the pre-surgery level and give adequate time for any cognitive effects resulting from the surgery itself to dissipate. The primary endpoint will compare changes in scores on the N-back test before and after surgery from those in the deiodinase CC polymorphism group to those in the deiodinase type 2 TC and TT groups. Secondary endpoints will include scores on the SART and well-being questionnaires before and after surgery to correlate with deiodinase polymorphisms as well as correlation of these outcome measures with serum thyronamine levels before and after surgery as an exploratory measure. 