Reference interval for thyrotropin in a ultrasonography screened Korean population

Area of Science:

• Endocrinology
• Clinical Chemistry
• Public Health

Background:

• Thyroid dysfunction diagnosis relies heavily on accurate serum thyroid-stimulating hormone (TSH) reference intervals.
• Existing TSH reference intervals are often based on Western populations, potentially leading to misdiagnosis in diverse ethnic groups.
• Establishing a population-specific TSH reference interval is crucial for improving diagnostic accuracy.

Purpose of the Study:

• To determine a precise reference interval for serum TSH in a normal Korean population.
• To investigate factors influencing serum TSH levels, including sex, age, smoking status, and thyroid autoimmunity.

Main Methods:

• Analysis of serum TSH levels in 19,465 Korean adults undergoing routine health check-ups.
• Exclusion of individuals with pre-existing thyroid conditions or family history of thyroid cancer.
• Definition of a normal reference population based on National Academy of Clinical Biochemistry guidelines, ultrasound findings, and smoking status.

Main Results:

• The established reference interval for serum TSH in the normal Korean population was 0.73 to 7.06 mIU/L.
• Serum TSH levels were significantly higher in females than males across all age groups.
• Smokers exhibited lower TSH levels, while positive anti-thyroid peroxidase antibodies or abnormal ultrasound findings widened the TSH interval.

Conclusions:

• The serum TSH reference interval for Koreans is higher than previously established Western-based intervals.
• Current Western-derived TSH upper and lower limits may require upward adjustment for the Korean population.
• Implementing a Korean-specific TSH reference interval can enhance the diagnostic accuracy of thyroid disorders in this population.