Development of Gestational Age-Specific Thyroid Function Test Reference Intervals in Four Analytic Platforms Through...

Area of Science:

• Endocrinology
• Reproductive Medicine
• Clinical Chemistry

Background:

• Accurate thyroid hormone reference intervals (RIs) during pregnancy are essential for clinical diagnosis and inter-platform result comparison.
• Standardized methodologies are needed to establish reliable gestational age-specific RIs for thyroid function tests.

Purpose of the Study:

• To establish population-based, gestational age-specific reference intervals for thyroid hormones in healthy Chinese pregnant women.
• To evaluate the influence of mild iodine deficiency and thyroid antibodies on these reference intervals.
• To propose a standardized methodology for constructing and comparing thyroid function test RIs across different analytical platforms.

Main Methods:

• Longitudinal serum samples were collected from 600 healthy Chinese women throughout gestation.
• Subjects with thyroid receptor antibodies were excluded; data from those with thyroid peroxidase and thyroglobulin antibodies were included.
• Gestational age-specific RIs were constructed using polynomial regression equations.

Main Results:

• Free thyroxine (fT4) peaked at 7-8 weeks and declined by week 28; thyrotropin (TSH) decreased to a nadir at week 9.
• The findings support the American Thyroid Association's recommendation to raise the TSH upper RI to 4.0 mIU/L.
• Thyroid hormone reference ranges were not significantly affected by mild iodine deficiency or the presence of thyroid peroxidase/thyroglobulin antibodies in otherwise healthy women.

Conclusions:

• A robust methodology for establishing gestational age-specific thyroid function test RIs was demonstrated.
• The study provides crucial reference data for thyroid hormone levels in pregnant Chinese women.
• The findings facilitate better interpretation and comparison of thyroid function test results across different analytic platforms.