In order to evaluate the mechanism of high growth hormone (GH) secretion in perinatal life, the levels of GH and growth-hormone-releasing factor (GRF) in cord blood were determined. Plasma-immunoreactive GRF was measured by a double antibody RIA method. The levels (mean ± SD) of GH, GRF and somatostatin (SRIF) were 23.4 ± 10.2 ng/ml, 49.5 ± 11.7 and 41.5 ± 10.4 pg/ml, respectively; they were remarkably higher than those of healthy adults. In Statistical analysis, there were no significant relationships among the levels of GH, GRF or SRIF. We speculate that a high GRF release from the hypothalamus might increase the secretion of GH in the perinatal period.

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The levels of corticotropin-releasing factor (CRF) in the cord blood from 34 infants were determined by radioimmunoassay. All infants were born by vaginal delivery after an uneventful pregnancy. Levels of cortisol, dehydroepiandrosterone sulfate and ACTH were high in the cord blood. CRF levels (mean ± SD) were 100.5 ± 31.7 and 44.5 ± 7.8 pg/ml, respectively, in cord blood and in controls (healthy prepubertal children, n = 10). Although the origin of CRF in peripheral circulation has not been clarified, we speculate that the high adrenocortical steroid synthesis of the fetus might be a consequence of high CRF levels in fetal circulation.

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