The Impact of Age- and Sex-Specific Reference Ranges for Serum Thyrotropin and Free Thyroxine on the Diagnosis of Subclinical Thyroid Dysfunction: A Multicenter Study from Japan
An erratum to this article was published (Thyroid, Sep 2023 ↗)
Authors' conclusion
Age- and sex-specific reference ranges should be used to avoid over- and underdiagnosis of subclinical thyroid dysfunction and appropriate therapies.
Study context
- Population
- Euthyroid individuals undergoing annual health check-ups at Takasaki Hidaka Hospital (Siemens and Abbott kits) and participants visiting a specialized thyroid-focused hospital (Tosoh kits), Japan
- Outcome
- Sex-specific 95% reference ranges for TSH and fT4 by age strata
Methodological detailsretrospective, multicentre, Siemens kit n=14,860 and Abbott kit n=8,132 (health check-ups); Tosoh kits n=515 (thyroid hospital)
- Retrospective
- Multicentre
- Siemens kit n=14,860 and Abbott kit n=8,132 (health check-ups); Tosoh kits n=515 (thyroid hospital)
Main finding
As reported in the abstract
Median TSH, women in their 30s, Siemens kit (2.5th; 97.5th percentile 0.5; 4.6)
1.5 mIU/L
Median TSH, women in their 60s, Siemens kit (0.7-7.8)
1.9 mIU/L
Median free thyroxine (fT4), men in their 30s (1.0-1.7)
1.3 ng/dL
Median fT4, men in their 60s (1.0-1.6)
1.2 ng/dL
Observational data: associations, not effects.
Further findings
Free triiodothyronine (fT3) levels
- fT3 significantly higher in men than women and gradually but significantly decreased with age
Reclassification of SCH in women (Siemens kit) with age- and sex-specific reference ranges
- Women with SCH by manufacturer-recommended ranges who had normal results with age- and sex-specific ranges
- ∼60% (216/358)
- Overdiagnosis especially in those aged ≥60 years
- Some middle-aged individuals with normal thyroid function reclassified as subclinical hyperthyroidism
Original publication
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