Vol 72, No 6 (2021)
Review paper
Published online: 2021-10-22

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Liothyronine use in primary hypothyroidism — current concepts

Marcio José Concepción-Zavaleta1, Sofía Pilar Ildefonso-Najarro2, José Luis Paz-Ibarra3, Freddy Roynall Valdivia Fernández-Dávila2, Diana Carolina Deutz Gómez-Condori2, Katia Eugenia Rivera-Fabián2, Ramiro Grimaldo Herrera-Cabezas4, Luis Alberto Concepción-Urteaga5
Pubmed: 34855197
Endokrynol Pol 2021;72(6):650-660.


Hypothyroidism is an endocrine disorder whose management raises many challenges in clinical practice. Its standard treatment is levothyroxine (LT4). The goal of the treatment is to normalize signs and symptoms, as well as to achieve thyroid-stimulating hormone (TSH) concentrations within the reference range, on an individual basis. It is known that 5–10% of hypothyroid patients remain symptomatic, despite achieving the target TSH levels, which, in turn, affects their quality of life. After ruling out other causes of non-thyroid origin for this persistence, it is suggested that these patients could benefit from the use of liothyronine (LT3), added to LT4, especially if polymorphism of the deiodinase 2 (D2) genes is documented. There exist a variety of LT3 preparations, whose concentrations vary from 5 to 50 ug, with the recommended LT4/LT3 ratio of 13:1–20:1. The goals of combination therapy should be to achieve a physiological ratio of free triiodothyronine/free thyroxine (FT3/FT4) and non-suppression of TSH. Because there is currently no guide that makes evidence-based recommendations on the use of LT3 in primary hypothyroidism, more clinical studies are needed to be able to identify hypothyroid patients who may benefit from the use of LT3, by identifying new biomarkers. 

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