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The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy

Thyroid hormone replacement for hypothyroidism can be achieved via several approaches utilizing different preparations of thyroid hormones, T3, and/or T4. “Combination therapy” involves administration of both T3 and T4, and was technically the first treatment for hypothyroidism. It was lauded as a c...

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Autores principales: McAninch, Elizabeth A., Bianco, Antonio C.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6629976/
https://www.ncbi.nlm.nih.gov/pubmed/31354624
http://dx.doi.org/10.3389/fendo.2019.00446
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author McAninch, Elizabeth A.
Bianco, Antonio C.
author_facet McAninch, Elizabeth A.
Bianco, Antonio C.
author_sort McAninch, Elizabeth A.
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description Thyroid hormone replacement for hypothyroidism can be achieved via several approaches utilizing different preparations of thyroid hormones, T3, and/or T4. “Combination therapy” involves administration of both T3 and T4, and was technically the first treatment for hypothyroidism. It was lauded as a cure for the morbidity and mortality associated with myxedema, the most severe presentation of overt hypothyroidism. In the late nineteenth and the early Twentieth centuries, combination therapy per se could consist of thyroid gland transplant, or more commonly, consumption of desiccated animal thyroid, thyroid extract, or thyroglobulin. Combination therapy remained the mainstay of therapy for decades despite development of synthetic formulations of T4 and T3, because it was efficacious and cost effective. However, concerns emerged about the consistency and potency of desiccated thyroid hormone after cases were reported detailing either continued hypothyroidism or iatrogenic thyrotoxicosis. Development of the TSH radioimmunoassay and discovery of conversion of T4-to-T3 in humans led to a major transition in clinical practices away from combination therapy, to adoption of levothyroxine “monotherapy” as the standard of care. Levothyroxine monotherapy has a favorable safety profile and can effectively normalize the serum TSH, the most sensitive marker of hypothyroidism. Whether levothyroxine monotherapy restores thyroid hormone signaling within all tissues remains controversial. Evidence of persistent signs and symptoms of hypothyroidism during levothyroxine monotherapy at doses that normalize serum TSH is mounting. Hence, in the last decade there has been acknowledgment by all thyroid professional societies that there may be a role for the use of combination therapy; this represents a significant shift in the clinical practice guidelines. Further bolstering this trend are the recent findings that the Thr92AlaD2 polymorphism may reduce thyroid hormone signaling, resulting in localized and systemic hypothyroidism. This strengthens the hypothesis that treatment options could be personalized, taking into consideration genotypes and comorbidities. The development of long-acting formulations of liothyronine and continued advancements in development of thyroid regenerative therapy, may propel the field closer to adoption of a physiologic thyroid hormone replacement regimen with combination therapy.
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spelling pubmed-66299762019-07-26 The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy McAninch, Elizabeth A. Bianco, Antonio C. Front Endocrinol (Lausanne) Endocrinology Thyroid hormone replacement for hypothyroidism can be achieved via several approaches utilizing different preparations of thyroid hormones, T3, and/or T4. “Combination therapy” involves administration of both T3 and T4, and was technically the first treatment for hypothyroidism. It was lauded as a cure for the morbidity and mortality associated with myxedema, the most severe presentation of overt hypothyroidism. In the late nineteenth and the early Twentieth centuries, combination therapy per se could consist of thyroid gland transplant, or more commonly, consumption of desiccated animal thyroid, thyroid extract, or thyroglobulin. Combination therapy remained the mainstay of therapy for decades despite development of synthetic formulations of T4 and T3, because it was efficacious and cost effective. However, concerns emerged about the consistency and potency of desiccated thyroid hormone after cases were reported detailing either continued hypothyroidism or iatrogenic thyrotoxicosis. Development of the TSH radioimmunoassay and discovery of conversion of T4-to-T3 in humans led to a major transition in clinical practices away from combination therapy, to adoption of levothyroxine “monotherapy” as the standard of care. Levothyroxine monotherapy has a favorable safety profile and can effectively normalize the serum TSH, the most sensitive marker of hypothyroidism. Whether levothyroxine monotherapy restores thyroid hormone signaling within all tissues remains controversial. Evidence of persistent signs and symptoms of hypothyroidism during levothyroxine monotherapy at doses that normalize serum TSH is mounting. Hence, in the last decade there has been acknowledgment by all thyroid professional societies that there may be a role for the use of combination therapy; this represents a significant shift in the clinical practice guidelines. Further bolstering this trend are the recent findings that the Thr92AlaD2 polymorphism may reduce thyroid hormone signaling, resulting in localized and systemic hypothyroidism. This strengthens the hypothesis that treatment options could be personalized, taking into consideration genotypes and comorbidities. The development of long-acting formulations of liothyronine and continued advancements in development of thyroid regenerative therapy, may propel the field closer to adoption of a physiologic thyroid hormone replacement regimen with combination therapy. Frontiers Media S.A. 2019-07-09 /pmc/articles/PMC6629976/ /pubmed/31354624 http://dx.doi.org/10.3389/fendo.2019.00446 Text en Copyright © 2019 McAninch and Bianco. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Endocrinology
McAninch, Elizabeth A.
Bianco, Antonio C.
The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy
title The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy
title_full The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy
title_fullStr The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy
title_full_unstemmed The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy
title_short The Swinging Pendulum in Treatment for Hypothyroidism: From (and Toward?) Combination Therapy
title_sort swinging pendulum in treatment for hypothyroidism: from (and toward?) combination therapy
topic Endocrinology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6629976/
https://www.ncbi.nlm.nih.gov/pubmed/31354624
http://dx.doi.org/10.3389/fendo.2019.00446
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