European Thyroid Association (ETA) and Thyroid Federation International (TFI) joint position statement on the interchangeability of levothyroxine products in EU countries
Open accessAbstract
Several European countries have seen major health issues after a switch from one levothyroxine brand to another, as well as following the introduction of several levothyroxine formulation changes. While the relationship between these health issues and brand or formulation changes merits further investigation, the current position statement on behalf of both health-care providers and patients summarizes recent events in several European countries and provides a number of recommendations to limit the burden for patients, so as to prevent increased health-care consumption and health-care expenses in this context.
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Adverse effects of switching levothyroxine brand included headaches, muscular fatigue, depression, anxiety, hair loss, and insomnia.
“These adverse effects included headaches, muscular fatigue, depression, anxiety, hair loss and insomnia.”
From ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism (2025) · cites this paper as [39]
The France section lists all six symptoms among adverse effects reported after patients switched to a new formulation of Merck’s Levothyrox. It describes a formulation change, not a switch of levothyroxine brand, and does not establish that the change caused the reported effects. (LLM, conf=0.88)
Experimental — accuracy not yet measuredOwing to uncertainties regarding levothyroxine bioequivalence of certain generics to branded compounds, some variation in patients' TSH levels was observed.
“Owing to some uncertainties regarding the levothyroxine bioequivalence of certain generics to that of branded compounds, some variation in patients’ TSH levels were observed (28, 39, 40).”
From ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism (2025) · cites this paper as [39]
The Introduction describes concerns about generic levothyroxine bioequivalence and recommends TSH testing after a switch from a brand to a generic. It also reports thyroid-test evidence of oversupplementation after a forced brand switch. The paper does not establish that uncertain bioequivalence between generics and branded products caused the observed TSH changes; its Conclusions say the biological role of formulation changes cannot be ascertained. Page numbers are not provided for these passages. (LLM, conf=0.85)
Experimental — accuracy not yet measuredIn European countries, the switch from one levothyroxine brand to another caused some health issues.
“In European countries, the switch from one levothyroxine brand to another caused some health issues (39).”
From ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism (2025) · cites this paper as [39]
The Conclusions report major health issues after levothyroxine brand switches in several European countries. But they say it is not possible to ascertain how many of those issues were biologically related to the changes, so the claim's causal wording is stronger than the source supports. (LLM, conf=0.88)
Experimental — accuracy not yet measuredOther studies found switching among generics is associated with clinically significant changes in TSH level.
“but not for others (28, 37, 39, 40).”
From ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism (2025) · cites this paper as [39]
The Conclusions report increased biochemical signs of inadequate dosing after levothyroxine brand or formulation changes, while acknowledging uncertainty about their relationship to the changes. The Introduction recommends TSH retesting after a generic-to-generic switch, but our copy does not report studies finding clinically significant TSH changes specifically from switching among generics. (LLM, conf=0.84)
Experimental — accuracy not yet measuredA Joint Position Statement from ETA and TFI affirmed that after a formulation change of levothyroxine, bioequivalence does not guarantee continued euthyroidism.
“A Joint Position Statement from the European Thyroid Association (ETA) and Thyroid Federation International (TFI) affirmed that after a formulation change of levothyroxine, bioequivalence does not guarantee continued euthyroidism (39).”
From ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism (2025) · cites this paper as [39]
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Cites
U.S. Food and Drug Administration's Decision Regarding Bioequivalence of Levothyroxine Sodium
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Research works printed but not linked: 1
- Fliers/Demeneix/Bhaseen/Brix Eur Thyroid J 2018;7:238-242 242 DOI: 10.1159/000493123
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- Authors
- Fliers, E., Demeneix, B., Bhaseen, A., & Brix, T. H.
- Affiliations
- Amsterdam UMC Location University of Amsterdam (NL)
- Centre National de la Recherche Scientifique (FR)
- Concordia University (CA)
- Odense University Hospital (DK)
- Corresponding author
- Brix, Thomas H.
- Venue
- European Thyroid Journal
- Publisher
- Bioscientifica
- Published
- 2018-09-28
- Volume
- 7
- Issue
- 5
- Pages
- 238-242
- ISSN
- 2235-0640 (ISSN-L)
- 2235-0802
- PMC
- PMC6198781
- OpenAlex
- W2892659340
- Cited by
- 26
- References
- 3
- Citations by year
- 2026: 2 · 2025: 1 · 2024: 2 · 2023: 4 · 2022: 7 · 2021: 3 · 2020: 5 · 2019: 2
- FWCI
- 1.99
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- European Thyroid Journal (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Pure Amsterdam UMC (publishedVersion, other-oa)
- Data Archiving and Networked Services (DANS) (submittedVersion)
- HAL (submittedVersion)
- University of Southern Denmark Research Portal (University of Southern Denmark) (submittedVersion, other-oa)
- Topics
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Pharmaceutical Economics and Policy
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Medical and Pharmaceutic Studies
- Keywords
- levothyroxine, drug interchangeability, brand switching, thyroid hormone replacement, adverse drug reactions, health care costs, patient burden, European Union
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