[The effects of propylthiouracil on the fetal thyroid and serum concentration in pregnant women].

In order to study the effects of propylthiouracil (PTU) on the fetal thyroid and serum concentration, 9 women undergoing therapeutic abortion at the second trimester of pregnancy were given a single dose of 50, 100 and 150 mg PTU respectively. The concentrations of PTU in the maternal and fetal serum and those in the fetal thyroid tissues were determined with a high-performance liquid chromatographic method, the lowest limit of which was 25 micrograms/L. After an oral bolus of PTU, the PTU concentrations in the maternal serum reached a peak level after one hour and there was a wide individual variation of the peak value. The study showed PTU could be transferred through the placenta from the maternal blood to the fetal blood and highly accumulated in the fetal thyroid tissues. The fetal serum PTU concentrations correlated with those of their mothers at the same time (r = 0.7084, P < 0.02) and the concentrations in the fetal thyroid tissues could be evaluated by the maternal serum peak level after an oral bolus. PTU didn't inhibit the fetal thyroid peroxidase activity even when the maternal serum PTU concentration reached 4 mg/L, which is the lowest effective therapeutic concentration of PTU in adults.