Levothyroxine Pseudomalabsorption and Thyroxine Absorption Testing with Use of High-Dose Levothyroxine: Case Report and Discussion
Abstract
Objective To report the case of a 55-year-old woman who had been prescribed a daily dose of 1,000 μg of levothyroxine for the treatment of hypothyroidism but still had severe biochemical hypothyroidism and to discuss the use of thyroxine absorption testing to diagnose pseudomalabsorption.Methods The patient was admitted to the hospital for supervised thyroxine absorption testing. Baseline thyroid function tests were performed. An oral dose of 1,000 μg of levothyroxine was administered while the patient had an empty stomach, and thyroid function tests were repeated at 2, 4, and 6 hours after administration. She was also given all her prescribed antihypertensive medications, and the blood pressure (which had been persistently high) was measured every 2 hours.Results After administration of 1,000 μg of levothyroxine, a rapid improvement in the results of her thyroid function tests was noted. Similarly, a rapid decrease in her blood pressure was observed after supervised administration of her antihypertensive medications. A diagnosis of nonadherence to treatment (pseudomalabsorption of levothyroxine) was made. After reduction of her levothyroxine dosage to 100 μg daily, results of thyroid function tests showed improvement. The doses of her antihypertensive medications were likewise altered.Conclusion We suggest that patients who are receiving doses of levothyroxine of more than 2 μg/kg of body weight, with persistently increased thyroid-stimulating hormone levels, should undergo testing for malabsorption and pseudomalabsorption of levothyroxine. Thyroxine absorption testing with use of high-dose levothyroxine is useful in diagnosing pseudomalabsorption but needs formal evaluation and validation.
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Pseudomalabsorption is a most common source of difficulties in obtaining euthyreosis in hypothyroid patients.
“pseudomalabsorption (which is a most common source of difficulties in obtaining euthyreosis in hypothyroid patients)”
From Diagnosis and management of treatment-refractory hypothyroidism: an expert consensus report (2017) · cites this paper as [117]
A high-dose levothyroxine absorption test can play an important role in the differential diagnosis of pseudomalabsorption and actual levothyroxine malabsorption.
“Using a high-dose levothyroxine, absorption test can play an important role in the differential diagnosis of pseudomalabsorption (which is a most common source of difficulties in obtaining euthyreosis in hypothyroid patients) and actual levothyroxine malabsorption [117, 118].”
From Diagnosis and management of treatment-refractory hypothyroidism: an expert consensus report (2017) · cites this paper as [117]
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- Authors
- Srinivas, V., & Oyibo, S. O.
- Affiliations
- National Health Service (GB)
- ORCID
- Oyibo, Samson O.
- Venue
- Endocrine Practice
- Publisher
- Elsevier BV
- Published
- 2010-11
- Volume
- 16
- Issue
- 6
- Pages
- 1012-1015
- ISSN
- 1530-891X (ISSN-L)
- OpenAlex
- W2083256140
- Cited by
- 23
- References
- 22
- Citations by year
- 2025: 1 · 2024: 1 · 2022: 1 · 2020: 1 · 2019: 3 · 2018: 2 · 2017: 3 · 2016: 2 · 2015: 3 · 2014: 1 · 2013: 1 · 2012: 4
- FWCI
- 1.21
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Endocrine Practice (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
- Health Sciences › Medicine › Family Practice › Medication Adherence and Compliance
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Adrenal Hormones and Disorders
- Keywords
- levothyroxine, hypothyroidism, treatment non-adherence, thyroid-stimulating hormone, antihypertensive drugs, blood pressure, thyroid function tests
- MeSH terms
- Female, Humans, Hypothyroidism, Middle Aged, Thyroid Function Tests, Thyroxine
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