Reference Intervals of Thyroid Hormones During Pregnancy Established by Three Statistical Methods.

Area of Science:

• Endocrinology
• Reproductive Medicine
• Clinical Chemistry

Background:

• Thyroid hormone monitoring is vital for fetal development.
• Thyroid hormone reference intervals (RIs) fluctuate significantly during pregnancy.
• Establishing accurate RIs is essential for managing thyroid function in pregnant individuals.

Purpose of the Study:

• To determine method- and trimester-specific reference intervals (RIs) for key thyroid hormones.
• To investigate thyroid-stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) levels in pregnant Chinese women.
• To compare different statistical methods for RI determination.

Main Methods:

• Recruited 2,167 pregnant women and 4,231 non-pregnant women.
• Measured serum TSH, fT4, and fT3 using electrochemiluminescence immunoassays.
• Determined RIs using non-parametric, Hoffmann, and Q-Q plot methods after outlier exclusion.

Main Results:

• Thyroid hormone levels in pregnant women significantly differ from non-pregnant individuals.
• Hormone concentrations varied considerably across the three trimesters of pregnancy.
• Non-parametric and Q-Q plot methods yielded comparable RIs, while the Hoffmann method produced wider and higher intervals.

Conclusions:

• Trimester-specific reference intervals are necessary for thyroid hormones during pregnancy.
• Non-parametric and Q-Q plot methods are suitable alternatives for calculating thyroid hormone RIs.
• Accurate RIs aid in the proper assessment of thyroid function in pregnant populations.