Evaluating the progression to abnormal thyrotropin in euthyroid preconception women: a population-based study

Area of Science:

• Endocrinology
• Reproductive Health
• Thyroid Function

Background:

• Abnormal preconception thyrotropin is linked to fertility and pregnancy complications.
• Limited data exists on natural thyrotropin changes in euthyroid women before conception.

Purpose of the Study:

• To evaluate the progression to abnormal thyrotropin levels in euthyroid women of reproductive age.
• To identify optimal preconception thyrotropin ranges for minimizing abnormal thyroid progression.

Main Methods:

• Retrospective cohort study using data from the National Free Prepregnancy Checkups Project (2010-2020).
• Included 186,095 euthyroid women with normal initial thyrotropin and 1.5-3.0 year follow-up.
• Analyzed thyrotropin changes and associated risks using statistical modeling.

Main Results:

• 4.57% of women developed abnormal thyrotropin (subnormal or supranormal).
• Lower and higher baseline thyrotropin levels correlated with increased risk of subnormal and supranormal levels, respectively.
• U-shaped and J-shaped dose-response associations were observed for subnormal and supranormal thyrotropin risks.

Conclusions:

• Both low and high baseline thyrotropin levels significantly increase the risk of developing abnormal thyrotropin.
• Optimal preconception thyrotropin levels may range from 1.43-1.93 mIU/L (or 0.59-1.36 MoM) to reduce progression to abnormal levels.
• Findings support improved preconception counseling and thyroid function monitoring.