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Fetal thyroid function
J G Thorpe-Beeston1, K H Nicolaides
1Department of Obstetrics and Gynaecology, St. Mary's Hospital, London, UK.
Cordocentesis has permitted the study of fetal thyroid function. In normal pregnancy, fetal blood thyroid-stimulating hormone (TSH), thyroid hormones and thyroid-binding globulin increase with advancing gestation demonstrating functional maturation of the pituitary, thyroid and liver, respectively. The administration of thyroid-releasing hormone to the mother produces a rapid increase in fetal TSH from at least 25 weeks gestation. In hypoxemic growth-retarded fetuses, the concentrations of TSH are higher, and the concentrations of total and free thyroxine are lower than in appropriately grown fetuses. In anemic fetuses from red cell-isoimmunized pregnancies, serum TSH and thyroid hormone concentrations are increased. In some chromosomally abnormal fetuses, particularly those with trisomy 21, TSH is increased.
Cordocentesis has permitted the study of fetal thyroid function. In normal pregnancy, fetal blood thyroid-stimulating hormone (TSH), thyroid hormones and thyroid-binding globulin increase with advancing gestation demonstrating functional maturation of the pituitary, thyroid and liver, respectively. The administration of thyroid-releasing hormone to the mother produces a rapid increase in fetal TSH from at least 25 weeks gestation. In hypoxemic growth-retarded fetuses, the concentrations of TSH are higher, and the concentrations of total and free thyroxine are lower than in appropriately grown fetuses. In anemic fetuses from red cell-isoimmunized pregnancies, serum TSH and thyroid hormone concentrations are increased. In some chromosomally abnormal fetuses, particularly those with trisomy 21, TSH is increased.