Response of growth hormone to thyrotropin-releasing hormone during fetal life.

The effect of TRH administration to the term pregnant women on the GH response in cord blood (CB) was evaluated in 138 subjects. Previous studies have demonstrated that TRH readily crosses the placenta. TRH (400 microgram) was administered iv to 59 pregnant women just before delivery. CB samples were obtained at delivery and assigned to 6 groups, depending upon the duration of time between TRH injection and CB sampling. The control group comprised 79 pregnant women who received saline. A progressive rise and then a fall in the CB GH concentration were observed after TRH administration. Values were significantly elevated 61-90 min after TRH administration compared to values in saline-treated subjects (19.3 +/- 3.1 vs. 13.1 +/- 0.9 ng/ml; P less than 0.05). The present study is the first report of the effect of TRH on the GH concentration in CB and suggests that TRH stimulates GH release in the fetus.