Amniotic fluid thyroid hormone concentrations during human gestation.
AFT4, AFT3, and AFrT3 concentrations were measured in samples from pregnant women between 10 and 43 weeks' gestation. During the first half of pregnancy, AFT4 and AFrT3 concentrations increased progressively, reaching peak levels at 25 to 30 and 17 to 20 weeks, respectively. AFT3 concentrations were low and increased slowly during this stage of pregnancy. During the last half of pregnancy, AFT4 and AFrT3 levels decreased while AFT3 continued to increase. This pattern of change is most likely explained by an increase in 5'-iodothyronine monodeiodinase activity in the fetal compartment. Normal values of amniotic fluid thyroid hormone concentrations as standards of reference for possible prenatal diagnosis of fetal thyroid abnormalities are provided.
D000653:Amniotic Fluid / Q000032:analysis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D013970:Thyronines / Q000032:analysis; D013974:Thyroxine / Q000032:analysis*
D013970:Thyronines; D013974:Thyroxine