Metformin does not suppress serum thyrotropin by increasing levothyroxine absorption
Open accessAbstract
BACKGROUND: Levothyroxine (LT4) absorption is affected by concomitant ingestion of certain minerals, medications, and foods. It has been hypothesized that metformin may suppress serum thyrotropin (TSH) concentrations by enhancing LT4 absorption or by directly affecting the hypothalamic-pituitary axis. This study examined the effect of metformin ingestion on LT4 absorption, as assessed by serum total thyroxine (TT4) concentrations. METHODS: A modified Food and Drug Administration LT4 bioequivalence protocol was applied to healthy, metformin-naïve, euthyroid adult volunteers. Following an overnight fast, 600 μg LT4 was administered orally. Serum TT4 concentrations were measured at baseline and at 0.5, 1, 1.5, 2, 4, and 6 h following LT4 administration. Measurements were performed before and after one week of metformin ingestion (850 mg three times daily). Peak serum TT4 concentrations, time to peak TT4 concentrations, and area under the concentration-time curve (AUC) were calculated. RESULTS: Twenty-six subjects (54% men, 27% white, age 33 ± 10 years) were studied. There were no significant differences in peak serum TT4 concentrations (p = 0.13) and time to peak TT4 concentrations (p = 0.19) before and after one week of metformin use. A trend toward reduced TT4 AUC was observed after metformin ingestion (pre-metformin 3893 ± 568 μg/dL-min, post-metformin 3765 ± 588 μg/dL-min, p = 0.09). CONCLUSIONS: LT4 absorption is unchanged by concomitant metformin ingestion. Mechanisms other than increased LT4 absorption may be responsible for the suppressed TSH concentrations observed in patients ingesting both drugs.
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Metformin suppresses TSH levels.
“Interestingly, metformin suppresses TSH levels (92, 93).”
From Levothyroxine: conventional and novel drug delivery formulations. (2023) · cites this paper as [92]
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- Authors
- Al-Alusi, M. A., Du, L., Li, N., Yeh, M. W., He, X., Braverman, L. E., & Leung, A. M.
- Affiliations
- UCLA David Geffen School of Medicine, Los Angeles, California.
- University of California, Los Angeles (US)
- Boston University (US)
- Corresponding author
- Leung, Angela M.
- Venue
- Thyroid
- Publisher
- SAGE Publications
- Published
- 2015-10
- Volume
- 25
- Issue
- 10
- Pages
- 1080-1084
- ISSN
- 1050-7256 (ISSN-L)
- 1557-9077
- PMC
- PMC4589100
- OpenAlex
- W2116671037
- Cited by
- 14
- References
- 31
- Citations by year
- 2023: 3 · 2022: 3 · 2020: 2 · 2019: 2 · 2018: 2 · 2017: 1 · 2016: 1
- FWCI
- 1.16
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- Thyroid (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- eScholarship (California Digital Library) (submittedVersion)
- Funders
- National Institutes of Health (UL1TR000124, CTSI UL1TR000124)
- National Center for Advancing Translational Sciences (UCLA CTSI UL1TR 000124, CTSI UL1TR000124)
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (K23HD068552)
- Clinical and Translational Science Institute, University of California, Los Angeles (UL1TR000124)
- Topics
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmacogenetics and Drug Metabolism
- Health Sciences › Medicine › Surgery › Thyroid and Parathyroid Surgery
- Keywords
- metformin, levothyroxine, drug absorption, TSH suppression, total thyroxine, drug-drug interactions, hypothalamic-pituitary axis
- MeSH terms
- Adult, Drug Interactions, Female, Humans, Hypoglycemic Agents, Male, Metformin, Thyrotropin, Thyroxine, Young Adult
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