L-carnitine and thyroid hormone tended to antagonize reciprocally in human body. Urinary
excretion of L-carnitine decreased in hypothyroid patients, and levothyroxine supplementation
increased excretion of L-carnitine. The investigators hypothesized that supplying L-carnitine
to hypothyroid patients with fatigue symptom could improve the quality of life, and fatigue
score in them. Therefore, the investigators planned to compare the efficacy of L-carnitine
and placebo in hypothyroid patients who had taken levothyroxine.