Somatomedin and growth hormone in the newborn.

Somatomedin (SM) levels were measured by porcine cartilage bioassay, and growth hormone (GH) levels by radioimmunoassay in 52 full-term umbilical cord plasma samples and 28 maternal plasma samples. The SM levels in cord plasmas was 0.50 +/- 0.19 units/ml (mean +/- SD) compared to an adult standard plasma pool of 1.0 units/ml. The cord GH levels were 41.7 +/- 36 mmicrogram/ml. The low relative value of SM in the cord plasma is consistent with that found during early childhood, and may reflect a lower level of requirement. The high neonatal GH levels are hypothesized to be a compensatory increase to overcome factors suppressing SM production in fetal life.