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Nuklearmedizin 2005; 44(02): 56-61
DOI: 10.1055/s-0038-1623926
Original Article
Schattauer GmbH

Where does subclinical hypothyroidism start?

Implications for the definition of the upper reference limit for thyroid stimulating hormoneWo beginnt die subklinische Hypothyreose?Implikationen zur Definition der oberen Referenzgrenze für Thyreotropin
K. Zöphel
1   Klinik für Nuklearmedizin (Direktor: Prof. Dr. med. Hans Döge), Klinikum Chemnitz gGmbH, Chemnitz
2   Klinik und Poliklinik für Nuklearmedizin (Direktor: Prof. Dr. med. Jörg Kotzerke), Universitätsklinikum Carl Gustav Carus der Technischen Universität Dresden, Deutschland
,
G. Wunderlich
1   Klinik für Nuklearmedizin (Direktor: Prof. Dr. med. Hans Döge), Klinikum Chemnitz gGmbH, Chemnitz
,
Th. Grüning
4   Department of Nuclear Medicine, Derriford Hospital, Plymouth, United Kingdom
,
R. Koch
3   Institut für Medizinische Informatik und Biometrie (Direktor: Prof. Dr. med. Hildebrand Kunath), Universitätsklinikum Carl Gustav Carus der Technischen Universität Dresden, Deutschland
,
H. Döge
1   Klinik für Nuklearmedizin (Direktor: Prof. Dr. med. Hans Döge), Klinikum Chemnitz gGmbH, Chemnitz
,
J. Kotzerke
2   Klinik und Poliklinik für Nuklearmedizin (Direktor: Prof. Dr. med. Jörg Kotzerke), Universitätsklinikum Carl Gustav Carus der Technischen Universität Dresden, Deutschland
› Author Affiliations
Further Information

Publication History

Eingegangen: 15 September 2004

11 October 2004

Publication Date:
11 January 2018 (online)

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Summary

The upper limit of the TSH reference range is currently under discussion. In its recent guidelines, the National Academy of Clinical Biochemistry (NACB) recommended the use of ~2.5 mIU/L, rather than ~4 mIU/L, due to the fact that reference populations, on which the definition of the reference range is based, contain persons undergoing an initial phase of autoimmune thyroid disease. This will skew the upper reference limit of TSH. Ultrasonography, in addition to measurement of thyroid autoantibodies, should be used to exclude these persons. Objective: The present study investigates whether the NACB recommendation also applies for a region of mild iodine deficiency. Methods: According to NACB criteria, a reference population (713 persons) was defined out of a total study population of 1442. The TSH reference range was calculated in this reference group and in further subgroups by percentiles. The results were compared with the total study population and the NACB recommendation. All assays used were provided by BRAHMS Diagnostica AG, Hennigsdorf, Germany. Results: As expected, all median TSH values, excluding the median of the group with a hypoechogenic thyroid were close to 1.2 mIU/L. The 97.5th percentile in the reference population was 3.35 mIU/L. However, there was no difference compared to the total study population. Conclusion: The upper reference limit for TSH based on a reference population according to NACB criteria came down to 3.35 mIU/L, but not to ~2.5 mIU/L. Interestingly, there is no difference compared to the total study population.

Zusammenfassung

Über die obere Grenze des Referenzbereichs für TSH wird lebhaft diskutiert. Die National Academy of Clinical Biochemistry (NACB) empfiehlt in ihren aktuellen Richtlinien die Absenkung derselben von derzeit ~4 mIU/l auf ~2,5 mIU/l mit der Begründung, dass die Referenzpopulationen, die der Referenzbereichsbestimmung zugrunde liegen, Personen enthalten, die bereits ein initiales Stadium einer Autoimmunthyreopathie durchlaufen. Dies verschiebt die obere Grenze des TSH-Referenzbereichs. Die Sonographie soll deshalb neben der Autoantikörperbestimmung zum Ausschluss solcher Personen herangezogen werden. Ziel: Diese Untersuchung soll klären, ob diese Empfehlung der NACB auf eine Region mit milder Ioddefizienz übertragbar ist. Methoden: Aus einem Gesamtkollektiv von 1442 Personen wurde eine Referenzpopulation (713 Personen) nach den NACB-Kriterien definiert. In diesem Referenzkollektiv und in weiteren Subgruppen erfolgte dann die Bestimmung des TSH-Referenzbereichs über Perzentilen. Diese wurden untereinander, mit dem Gesamtkollektiv und der NACB-Empfehlung verglichen. Alle Assays stammten von der Firma BRAHMS Diagnostica AG, Hennigsdorf. Ergebnisse: Erwartungsgemäß lagen alle medianen TSH-Werte, bis auf den der Gruppe mit sonographisch echoarmer Schilddrüse (1,78 mIU/l), um 1,2 mIU/l. Die 97,5. Perzentile in der Referenzpopulation wurde mit 3,35 mIU/l bestimmt. Allerdings unterschied sich dieser Wert nicht von dem des Gesamtkollektivs. Schlussfolgerung: Die obere Grenze des TSH-Referenzbereichs wird in einem nach den Kriterien der NACB definierten Referenzkollektiv mit 3,35 mIU/l zwar niedriger, jedoch nicht bei ~2,5 mIU/l, gefunden. Interessanterweise findet sich diesbezüglich kein Unterschied zwischen Referenz- und Gesamtkollektiv.

Keywords

Thyroid stimulating hormone - subclinical hypothyroidism - TSH reference range - thyroid gland

Schlüsselwörter

Thyreotropin - TSH-Referenzbereich - subklinische Hypothyreose - Schilddrüse
 

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