Experimental: Levothyroxine

Patients will be randomized to levothyroxine or placebo (similar in size, shape, and color to levothyroxine) via permuted blocks stratified by two TSH levels (\>3.0-5.0 and 5.0-10.0mIU/L) to ensure treatment balance across TSH levels. The study medications will be prepared in pill form. In the treatment arm, initial L-T4 doses will be 25mcg vs. 50mcg among patients whose TSH is \>3.0-5.0mIU/L vs. 5.0-10.0mIU/L, respectively. Patients in the placebo arm will receive an equivalent number of placebo pills daily depending upon TSH level.~The intervention period is 24 weeks. Patients will undergo up to two subsequent dose titrations after 8- and 16-weeks of treatment, based on interim TSH measurements at these time points. Patients whose TSH levels are higher or lower than the therapeutic TSH target of 0.5-3.0mIU/L will undergo a dose adjustment (+/- 25mcg), while those whose TSH levels are in target range will continue the prior dose.

Placebo_comparator: Placebo

Patients will be randomized to levothyroxine or placebo (similar in size, shape, and color to levothyroxine) via permuted blocks stratified by two TSH levels (\>3.0-5.0 and 5.0-10.0mIU/L) to ensure treatment balance across TSH levels. The study medications will be prepared in pill form. In the treatment arm, initial L-T4 doses will be 25mcg vs. 50mcg among patients whose TSH is \>3.0-5.0mIU/L vs. 5.0-10.0mIU/L, respectively. Patients in the placebo arm will receive an equivalent number of placebo pills daily depending upon TSH level.~The intervention period is 24 weeks. Patients in the placebo arm will undergo an equivalent titration in placebo pills (as that of the experimental arm) after 8- and 16-weeks of treatment, based on interim TSH measurements at these time points.