Age- and race-based serum thyrotropin reference limits.

Area of Science:

• Endocrinology
• Clinical Chemistry
• Population Health

Background:

• Thyroid-stimulating hormone (TSH) reference limits are controversial, with traditional methods assuming universal applicability.
• The standard approach uses TSH distribution from thyroid disease-free individuals, which is often skewed and may not represent all subpopulations accurately.
• Recent evidence suggests distinct subpopulations possess unique TSH distributions and reference limits.

Purpose of the Study:

• To review the basis of current TSH reference limit recommendations.
• To examine evidence indicating the traditional method's inadequacy for distinct subpopulations in the United States.
• To highlight the need for revised TSH reference limit strategies.

Main Methods:

• Literature search focusing on studies establishing current TSH reference limits.
• Inclusion of articles questioning the traditional method's accuracy for diverse groups.
• Analysis of research on TSH distribution variations across different demographics.

Main Results:

• TSH reference limits increase with age, extending to centenarians.
• Significant differences in TSH distribution exist among racial/ethnic groups, with higher levels in Caucasians compared to Black or Hispanic individuals.
• The traditional composite TSH distribution curve fails to provide appropriate reference limits for specific subpopulations.

Conclusions:

• Age- and race-specific TSH reference limits are necessary for accurate clinical interpretation.
• Genetic factors may influence TSH distribution, further necessitating tailored reference ranges.
• Implementing population-specific limits will improve the evaluation of thyroid dysfunction.