Supplementing liothyronine to levothyroxine therapy for management of hypothyroidism: Current clinical practice and beyond

Abstract

Hypothyroidism, the most prevalent endocrine disorder, is typically diagnosed by elevated serum thyrotropin (TSH) and low thyroxine (T4) levels. However, even when TSH levels normalize with standard levothyroxine (LT4) therapy, some patients continue to suffer from persistent symptoms. This review addresses the challenges in diagnosing and treating hypothyroidism, with a focus on the enduring symptoms encountered despite standard treatment. It also delves into the potential benefits of combining LT4 therapy with LT3 liothyronine (LT3). The non-specific nature of hypothyroid symptoms makes accurate diagnosis a challenge. A subset of patients comprising 5% to 15% of hypothyroid patients have poor quality of life due to residual symptoms of hypothyroidism. Such patients complain of symptoms including brain fog, depression and inability to lose weight despite normalization of TSH by levothyroxine therapy. This review emphasizes the potential advantages of adding LT3 to LT4 therapy, particularly for subgroups of patients experiencing ongoing symptoms despite normal TSH levels. Furthermore it highlights the need for accurate diagnosis and personalized treatment, as well as the potential of combining therapies to alleviate symptoms for certain patients.