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Cited by 23Thyroid Disorders and TreatmentsClinical Laboratory Practices and Quality ControlThyroid and Parathyroid Surgery

Measurements of Free Thyroxine: Comparison of Per Cent of Free Thyroxine in Diluted and Undiluted Sera

UCHIMURA, HIDEMASA, NAGATAKI, SHIGENOBU, TABUCHI, TOORU, MIZUNO, MASAHIKO, INGBAR, SIDNEY H.·1976·The Journal of Clinical Endocrinology & Metabolism
DOI 10.1210/jcem-42-3-561
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Abstract

The effect of dilution on values of the per cent of free T4 in serum (%FT4), measured by equilibrium dialysis, was determined by comparing the values for %FT4 in diluted and undiluted specimens. The specimens studied were sera obtained from 10 normal subjects, 10 patients with hyperthyroidism, 5 with hypothyroidism, and 9 women with normal pregnancy. The method of analysis employed was that described by Sterling and Brenner, except that the 125I-thyroxine used was predialyzed to remove non-thyroxine contaminants and that “corrected” values for %FT4 were calculated by dividing measured values by the numerical extent to which the serum had been diluted. Studies in a normal serum pool revealed that corrected values for %FT4 decreased with increasing dilution of serum, up to a dilution of 1:12, after which no significant further change occurred. In each of the various patient groups studied, for corrected %FT4 in sera diluted 1:12 were about 70% of those in undiluted serum, and the correlation coefficient of values obtained in individual specimens by the 2 methods was 0.91 (P < 0.001). These findings indicate that the proportionate relationship between values yielded by the 2 methods remains nearly constant over a wide range of alterations in the thyroid hormone-serum protein-binding interaction. In ancillary studies, indirect indices of absolute free T4 concentration, i.e., the “T7” value (Abbott) and the Effective Thyroxine Ratio (Mallinkrodt) were found to correlate closely with those obtained by equilibrium dialysis over the same range of abnormal binding interactions.

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Crossref · 10.1210/jcem-42-3-561

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Authors
UCHIMURA, H., NAGATAKI, S., TABUCHI, T., MIZUNO, M., & INGBAR, S. H.
Affiliations
  • The University of Tokyo (JP)
  • Harvard University (US)
Corresponding author
NAGATAKI, SHIGENOBU
ORCID
NAGATAKI, SHIGENOBU
Venue
The Journal of Clinical Endocrinology & Metabolism
Publisher
The Endocrine Society
Published
1976-03
Volume
42
Issue
3
Pages
561-566
ISSN
  • 0021-972X (ISSN-L)
  • 1945-7197
DOI
10.1210/jcem-42-3-561
OpenAlex
W2088364965
Cited by
23
References
12
Citations by year
2023: 1
FWCI
2.58
Type
journal article
Language
en
Open access
closed
Locations
  • The Journal of Clinical Endocrinology & Metabolism (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Health Sciences › Medicine › Physiology › Clinical Laboratory Practices and Quality Control
  • Health Sciences › Medicine › Surgery › Thyroid and Parathyroid Surgery
Keywords
free thyroxine, serum dilution, equilibrium dialysis, thyroid hormone binding, hyperthyroidism, hypothyroidism, pregnancy
MeSH terms
Female, Humans, Hyperthyroidism, Pregnancy, Thimerosal, Thyroid Function Tests, Thyroxine

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