Cited by 27Thyroid Disorders and TreatmentsThyroid and Parathyroid SurgeryThyroid Cancer Diagnosis and Treatment

Optimal Free Thyroxine Levels for Thyroid Hormone Replacement in Hypothyroidism

Iverson, Jennifer F., Mariash, Cary N.·2008·Endocrine Practice

Abstract

Objective To determine whether a difference exists in the free thyroxine level required to achieve a normal thyrotropin (thyroid-stimulating hormone or TSH) level between patients with primary hypothyroidism and euthyroid control subjects and compare the free thyroxine levels in patients with primary and secondary hypothyroidism receiving thyroid hormone replacement.Methods We retrospectively assessed TSH and free thyroxine values in 58 patients with primary hypothyroidism and 78 euthyroid control subjects for whom screening thyroid function tests had been performed. From the medical records, we also obtained free thyroxine values for 23 patients with central hypothyroidism receiving stable levothyroxine replacement therapy.Results The mean free thyroxine level was significantly higher in patients with primary hypothyroidism than in euthyroid control subjects (1.36 +/- 0.201 ng/dL versus 1.10 +/- 0.155 ng/dL, respectively; P<or=.0001), whereas the corresponding mean TSH concentrations did not differ significantly (1.60 +/- 1.183 mIU/L versus 1.73 +/- 0.792 mIU/L; P = .46). The mean free thyroxine value was also significantly higher in the patients with central hypothyroidism in comparison with that in the euthyroid control subjects (1.31 +/- 0.278 ng/dL versus 1.10 +/- 0.155 ng/dL, respectively; P<or=.0001), and no significant difference was noted between the patients with primary and central hypothyroidism (1.36 ng/dL versus 1.31 ng/dL; P = .60).Conclusion Patients with hypothyroidism require a higher level of serum free thyroxine to achieve a normal TSH value in comparison with euthyroid control subjects. This finding suggests that patients with central hypothyroidism should be treated to achieve free thyroxine levels in the upper part of the reference range.

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Crossref · 10.4158/ep.14.5.550

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Authors
Iverson, J. F., & Mariash, C. N.
Affiliations
  • Abbott Northwestern Hospital (US)
  • University of Minnesota (US)
Corresponding author
Mariash, Cary N.
Venue
Endocrine Practice
Publisher
Elsevier BV
Published
2008-07
Volume
14
Issue
5
Pages
550-555
ISSN
1530-891X (ISSN-L)
OpenAlex
W2116474364
Cited by
27
References
24
Citations by year
2025: 1 · 2024: 1 · 2023: 1 · 2021: 1 · 2019: 6 · 2018: 2 · 2017: 2 · 2016: 1 · 2015: 2 · 2014: 3 · 2012: 5
FWCI
0.48
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 › Surgery › Thyroid and Parathyroid Surgery
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Cancer Diagnosis and Treatment
Keywords
free thyroxine, thyroid hormone replacement, hypothyroidism, primary hypothyroidism, central hypothyroidism, thyroid-stimulating hormone, levothyroxine, thyroid function tests, reference values
MeSH terms
Adult, Female, Humans, Hypothyroidism, Male, Middle Aged, Retrospective Studies, Thyrotropin, Thyroxine, Hormone Replacement Therapy

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