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[Thyroid functional changes of normal human fetus and newborns].
Yun Zhao1, Li-jiang Zhang, Yan-qiu Wei
1Department of Obstetrics and Gynecology, People's Hospital, Beijing University, Beijing 100044, China.
Zhonghua Fu Chan Ke Za Zhi
|December 19, 2003
Summary
Fetal thyroid hormone levels, including thyroxine (T4) and free thyroxine (FT4), increase with gestational age. Monitoring these hormones is crucial for diagnosing congenital thyroid issues in the second half of pregnancy.
Area of Science:
- Endocrinology
- Perinatology
- Fetal Medicine
Context:
- Thyroid hormones are essential for fetal development.
- Accurate assessment of fetal thyroid function is critical for identifying potential health issues.
- Existing data on normal fetal thyroid hormone ranges during gestation is limited.
Purpose:
- To investigate the dynamic changes in fetal and newborn thyroid hormone levels throughout gestation.
- To establish reference ranges for key thyroid hormones (T4, T3, FT4, FT3, TSH) in fetuses and newborns.
- To inform the diagnosis and management of congenital fetal thyroid dysfunction.
Summary:
- Thyroid hormone levels (T4, T3, FT4, FT3, TSH) were measured in 71 fetuses between 16-36 weeks gestation via cordocentesis and compared to 140 term newborns.
- All measured thyroid hormones were detectable by 16 weeks gestation, with FT4 reaching adult levels.
- Thyroid hormone concentrations, particularly T4, T3, and FT4, showed a significant increase after 28 weeks gestation, while TSH levels gradually rose, peaking at birth.
Impact:
- Provides essential reference data for normal fetal thyroid hormone concentrations across gestational ages.
- Aids in the intra-uterine diagnosis and management of fetal thyroid disorders.
- Suggests that screening for congenital thyroid malfunction may not be optimal at 72 hours postpartum due to TSH peaking at birth.