Comorbidities, Concomitant Medications, and Diet as Factors Affecting Levothyroxine Therapy: Results of the CONTROL Surveillance Project
Open accessAbstract
BACKGROUND: The CONTROL Surveillance Project was a comprehensive patient-based survey conducted among hypothyroid patients undergoing treatment. The primary objective of the study was to specifically quantify the prevalence of factors adversely affecting levothyroxine therapy. METHODS: Participants were selected from a large proprietary database. Those eligible for the study completed a 21-question survey. RESULTS: Of the eligible hypothyroid patients, 925 (92.5%) were being treated with levothyroxine monotherapy. The mean age was 60.4 years; 755 (81.6%) were female and 168 (18.2%) were male. Almost half of those receiving levothyroxine (435, 47.0%) had at least one comorbid condition that could adversely affect its absorption: gastroesophageal reflux disease (33.8% of patients), irritable bowel syndrome (9.7%), lactose intolerance (7.8%), or a history of gastric bypass surgery or bowel resection (3.0%). Other factors reported by many patients that could adversely affect levothyroxine absorption included use of prescription medications (20.6%) and over-the-counter medications (34.3%) used to treat comorbid gastrointestinal (GI) conditions; use of dietary supplements (51.8%, primarily calcium and iron); and intake of foods/beverages high in fiber, iodine, or soy (68.0%). Of the 13.4% who reported difficulty controlling their hypothyroid symptoms, significantly more patients with comorbid GI conditions reported such difficulty (7.8 versus 5.6%, P < 0.01). Frequent changes in levothyroxine dosing (two or more dose changes in the past year) were reported by 8.0% of survey participants. Those with GI comorbidities were nearly twice as likely to have such changes (5.0 versus 3.0%, P < 0.01). CONCLUSION: Better initial workup of patients, including identification of relevant GI comorbidities and allergies, may help in the early detection of factors that may affect the performance of levothyroxine.
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In the CONTROL Surveillance Project among 925 patients on levothyroxine, more than 21% reported taking thyroxine less than the recommended 30 min before eating, a practice that may significantly contribute to less-than-optimal drug absorption.
“More than 21% reported taking thyroxine less than the recommended 30 min before eating, a practice that may significantly contribute to less-than-optimal drug absorption”
From Diagnosis and management of treatment-refractory hypothyroidism: an expert consensus report (2017) · cites this paper as [42]
Dietary soya and supplements, such as those containing calcium or iron, may interfere with the absorption of levothyroxine and thus increase TSH.
“Dietary soya and supplements, such as those containing calcium or iron, may interfere with the absorption of levothyroxine and thus increase TSH [33].”
From Challenges in Interpreting Thyroid Stimulating Hormone Results in the Diagnosis of Thyroid Dysfunction (2019) · cites this paper as [33]
Not waiting at least 30 minutes before breakfast after levothyroxine, or taking it with a beverage other than water, may reduce levothyroxine absorption.
“Failing to observe a minimum interval of 30 min before having breakfast after administering the LT4 dose, 33 or consuming it not solely with water, but alongside another beverage, [34][35][36][37] are circumstances that may impede the absorption of LT4.”
From Refractory hypothyroidism: unraveling the complexities of diagnosis and management (2023) · cites this paper as [33]
A high proportion of LT4-treated patients ingest medications, foodstuffs, and food supplements that selectively or specifically reduce intestinal absorption of LT4.
“Furthermore, a high proportion of LT4-treated patients ingest medications, foodstuffs and food supplements that selectively or specifically reduce the intestinal absorption of LT4.”
From Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults (2022) · cites this paper as [48]
A high proportion of LT4-treated patients have a disease or condition (e.g., gastroesophageal reflux disease, irritated bowel syndrome, food allergies, lactose intolerance, gastric bypass, H. pylori infection, gastroparesis, coeliac disease, ulcerative colitis, Crohn's disease, atrophic gastritis) that can reduce intestinal absorption of LT4.
“It is now clear that a high proportion of LT4-treated patients have a disease or condition (gastroesophageal reflux disease, irritated bowel syndrome, food allergies, lactose intolerance, gastric bypass, H. pylori infection, gastroparesis, coeliac disease, ulcerative colitis, Crohn’s disease, atrophic gastritis, etc.) that can reduce the intestinal absorption of LT4 [ 24 , 48 ].”
From Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults (2022) · cites this paper as [48]
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References 49 · Cited by 64
Research works printed but not linked: 1
- [21]US Food and Drug Administration. International Conference on Harmonisation; good clinical practice: consolidated guideline; availability. Federal Register. 1997;62:25692–709.
- Authors
- McMillan, M., Rotenberg, K. S., Vora, K., Sterman, A. B., Thevathasan, L., Ryan, M. F., Mehra, M., & Sandulli, W.
- Affiliations
- University of Oxford (GB)
- Corresponding author
- McMillan, Marjorie
- Venue
- Drugs in R&D
- Published
- 2015-12-21
- Volume
- 16
- Issue
- 1
- Pages
- 53-68
- ISSN
- 1174-5886 (ISSN-L)
- 1179-6901
- PMC
- PMC4767717
- OpenAlex
- W2221982530
- Cited by
- 64
- References
- 49
- Citations by year
- 2026: 4 · 2025: 8 · 2024: 7 · 2023: 6 · 2022: 5 · 2021: 9 · 2020: 5 · 2019: 7 · 2018: 4 · 2017: 6 · 2016: 3
- FWCI
- 3.76
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Drugs in R&D (publishedVersion, cc-by-nc)
- Europe PMC (PubMed Central) (publishedVersion, cc-by-nc)
- PubMed Central (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- Funders
- Akrimax Pharmaceuticals, LLC
- Topics
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Health Sciences › Medicine › Surgery › Thyroid and Parathyroid Surgery
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Cancer Diagnosis and Treatment
- Keywords
- levothyroxine, hypothyroidism, drug absorption, comorbidities, gastroesophageal reflux disease, irritable bowel syndrome, lactose intolerance, gastric bypass, concomitant medications, over-the-counter drugs, dietary supplements, dietary fiber, iodine, soybean, dose changes, symptom management
- MeSH terms
- Diet, Female, Humans, Hypothyroidism, Male, Middle Aged, Surveys and Questionnaires, Thyroxine, Comorbidity, Dietary Supplements
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