Effects of Pharmacological Fiber Supplements on Levothyroxine Absorption
Abstract
To determine the effect of pharmacological fiber supplements, we measured levothyroxine (LT 4 ) absorption without and with simultaneous ingestion of either calcium polycarbophil or psyllium hydrophilic mucilloid. Serum thyroxine (T 4 ) levels in 8 volunteers were measured following ingestion of 600 μg of LT 4 on 3 separate occasions at 4-week intervals: (1) LT 4 alone; (2) LT 4 together with 1000 mg polycarbophil; and (3) LT 4 together with 3.4 g psyllium. The amount of absorbed LT 4 was calculated as the incremental rise in serum T 4 level during the first 6 hours multiplied by the volume of distribution for the hormone, and expressed as a percentage of the dose administered. Absorption of LT 4 alone averaged 89% (95% confidence interval [CI]: 75%-104%), occurring at a median of 180 minutes. After simultaneous ingestion of calcium polycarbophil, LT 4 absorption was 86% (95% CI: 74%-97%), occurring at 180 minutes. With simultaneous ingestion of psyllium and LT 4 , the absorption was 80% (95% CI: 64%-95%), occurring at 240 minutes. In summary, neither calcium polycarbophil nor psyllium hydrophilic mucilloid are likely to cause malabsorption of LT 4 that could be detected by these methods.
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Fiber did not appear to affect absorption in a study of LT4 in healthy volunteers.
“However, fiber did not appear to affect absorption in a study of LT4 in healthy volunteers (127).”
From Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement (2014) · cites this paper as [127]
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- Authors
- Chiu, A. C., & Sherman, S. I.
- Affiliations
- The University of Texas MD Anderson Cancer Center (US)
- ORCID
- Sherman, Steven I.
- Venue
- Thyroid®
- Publisher
- SAGE Publications
- Published
- 1998-08
- Volume
- 8
- Issue
- 8
- Pages
- 667-671
- ISSN
- 1050-7256 (ISSN-L)
- 1557-9077
- OpenAlex
- W2040822880
- Cited by
- 41
- References
- 26
- Citations by year
- 2025: 1 · 2023: 2 · 2022: 2 · 2021: 2 · 2018: 2 · 2017: 1 · 2016: 2 · 2015: 1 · 2014: 3 · 2013: 3 · 2012: 1
- FWCI
- 0.45
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Thyroid (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmaceutical Science › Drug Solubulity and Delivery Systems
- Health Sciences › Nursing › Nutrition and Dietetics › Food composition and properties
- Keywords
- levothyroxine, drug absorption, dietary fiber, psyllium, serum thyroxine, malabsorption, antithyroid drugs, food-drug interactions
- MeSH terms
- Acrylic Resins, Adult, Female, Humans, Intestinal Absorption, Male, Psyllium, Radioimmunoassay, Thyrotropin, Thyroxine
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