Patient's question:
NoDoctor's answer:
Because fetal development requires FT4 (FT3 does not cross the placenta), it is necessary to ensure that the fetus has sufficient FT4. Currently, FT4 should be slightly above the midline. However, FT4 measurements have a large margin of error, so TSH is used for correction. A TSH level below 2.5 generally indicates that FT4 is sufficient. Of course, this is not absolute. As long as FT4 is adequate, TSH levels around 2.5 should still be considered normal.