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Nuklearmedizin 1985; 24(03): 115-121
DOI: 10.1055/s-0038-1624289
Short Communications – Kurzmitteilungen
Schattauer GmbH

The Evaluation of Free Thyroid Hormones (FT4 and FT3) in the Routine Diagnosis of Thyroid Function

Bewertung der freien Schilddrüsenhormone (FT4 und FT3) in der Schilddrüsen- Funktionsroutinediagnostik
A Passath
1   From the Medizinische Universitätsklinik (Vorstand: Prof. Dr. S. Sailer), Graz, Austria
,
G. Leb
1   From the Medizinische Universitätsklinik (Vorstand: Prof. Dr. S. Sailer), Graz, Austria
,
R. Goebel
1   From the Medizinische Universitätsklinik (Vorstand: Prof. Dr. S. Sailer), Graz, Austria
› Author Affiliations
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Publication History

Received: 10 September 1984

14 March 1985

Publication Date:
20 January 2018 (online)

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Summary

The validity of the free thyroid hormone parameters (FT4 and FT3) was verified in a random sample of 154 ambulatory patients with thyroid conditions. The “euthyroid range” of FT4 was between 15.67 and 30.66 pmol/1; median 21.98 pmol/1. The distribution of the FT4 readings peaked on the left and sloped to the right (log normal). In our laboratory, the “euthyroid reference range” of FT4 is between 10-28 pmol/1. The “euthyroid range” of FT3 extended from 4.6 to 9.7 pmol/ 1; median 6.63 pmol/1. The distribution of the readings was likewise log normal. The values of FT4 and FT3 are not significantly influenced by TBG concentration anomalies in otherwise healthy thyroid patients. For purposes of discrimination between euthyroidism and hyperthyroidism, FT3 (95%) and FT4 (90%) are better suited than the corresponding quotients for the free hormone fraction or the total hormone concentrations. On the other hand, the free hormone parameters are less suitable for the diagnosis of hypothyroidism. These results were deduced theoretically from mathematical function analyses between the TBG-independent free hormone parameters and the TBG-dependent hormone concentrations.

Zusammenfassung

Anhand einer Stichprobe von 154 ambulanten Schilddrüsenpatienten wurde die Wertigkeit der freien Schilddrüsenhormonparameter (FT4 und FT3) überprüft. Der »Euthyreosebereich« des FT4 dieser Stichprobe war zwischen 15,67 und 30,66 pmol/1; Median 21,98 pmol/1 (95% Vertrauensbereich). Die Verteilung der FT4 Meßwerte war linksgipfelig und rechtsschief (lognormal). Der laboreigene »euthyreote Referenzbereich« des FT4 liegt zwischen 10 und 28 pmol/1. Der »Euthyreosebereich« des FT3 reichte von 4,6-9,7 pmol/1; Median 6,63 pmol/1. Die Verteilung der Meßdaten war ebenfalls lognormal. Die Meßergebnisse des FT4 und FT3 werden durch TBG-Konzentrationsanomalien bei ansonst gesunden Schilddrüsenpatienten nicht signifikant beeinflußt. Zur Diskriminierung zwischen einer Euthyreose und einer Hyperthyreose sind das FT3 (95%) und das FT4 (90%) besser geeignet als die entsprechenden Quotienten für den freien Hormonanteil bzw. die Gesamthormonkonzentrationen. Zur Diskriminierung einer Hypothyreose sind die freien Hormonparameter weniger geeignet. Diese Ergebnisse wurden anhand mathematischer Funktionsanalysen zwischen den TBG-unabhängigen freien Hormonparametern und den TBG-abhängigen Hormonkonzentrationen theoretisch abgeleitet.

 

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