Dynamic evaluation of prolactin secretion during the early hours of life in human newborns.

PRL secretion was evaluated in 30 human newborns during the early hours of life. Both levodopa and pyridoxine administration failed to suppress PRL release in all subjects. Synthetic TRH elicited a constant, prompt increase in PRL levels. No significant changes were observed after somatostatin injections. These results demonstrate normal pituitary PRL reserve in newborns. The failure to respond to levodopa and pyridoxine administration might reflect partial immaturity of the pituitary dopaminergic receptors.