Role of T3 in Management of Hypothyroidism

The management of hypothyroidism is based on the assumption that levothyroxine monotherapy normalizes thyroid hormone homeostasis, rendering patients clinically and biochemically euthyroid. However, a subset of patients treated with levothyroxine (LT4) are dissatisfied as they continue to have symptoms such as fatigue, weight gain, and difficulty in concentration. Some patients do not achieve normalization of thyroid-stimulating hormone despite adherence to adequate LT4 dosing. It has been proposed that liothyronine (LT3) may benefit such patients. This review addresses the specific role of LT3 in the management of hypothyroidism with an emphasis on practical considerations and a focus on appropriate patient selection. It identifies clinical challenges where patient outcomes are improved by adding LT3 to LT4 therapy, including myxedema coma, preoperative management, and situations where swift resolution of hypothyroidism is warranted. Further, it addresses the challenges faced in dose titration of LT4 and LT3 and the importance of monitoring therapy with LT3.