Thyrotropin-releasing hormone and thyroid hormones in amniotic fluid

Immunoassayable TRH (iTRH) was measured in 50 amniotic fluid specimens with a mean concentration of 207 +/- 26 (SE) pg/ml. This iTRH demonstrates parallelism with the standard curve for synthetic TRH. With increasing gestational age there is an increase in iTRH levels in amniotic fluid with a decrease in 3,3',5'-triiodothyronine levels (rT3), while thyroxine levels (T4) remain unaltered. Preliminary data suggest that iTRH levels in amniotic fluid that are less than 150 pg/ml after 32 weeks of gestation may correlate well with low Apgar scores at birth. There was no correlation of rT3 or T4 amniotic fluid levels with the Apgar scores.