DOPAMINE INHIBITS GROWTH-HORMONE AND PROLACTIN SECRETION IN THE HUMANNEWBORN

Dopamine is frequently used in neonatal intensive care for its vasopre ssor, renal vasodilating, and cardiac inotropic properties, The effect of i.v, dopamine infusion on neonatal pituitary hormone secretion is currently unknown, We observed strikingly low serum concentrations of growth hormone (GH) and prolactin (PRL) during a therapeutic, standard ized, isovolumetric, partial exchange transfusion (blood sampling ever y 20 min for 6 h) in two polycythemic neonates requiring intensive the rapy, including continuous dopamine infusion, In addition, the secreti on of GH and PRL was studied in three neonates with symptomatic polycy themia (gestational age 34-38 wk; birth weight 2110-2530 p; postnatal age 10-30 h) during a partial exchange transfusion, including an inter vening dopamine infusion (8 mu g/kg/min i.v, for 2 h), The GH and PRL profiles were evaluated by deconvolution analysis, Initially, the thre e newborns exhibited high-amplitude, pulsatile GH secretion and contin uously elevated PRL release, During the dopamine infusion, GH secretio n was virtually abolished and PRL release was reduced by at least 50%, Dopamine withdrawal was associated with a rebound release of GH and P RL. Finally, serum GH and PRL concentrations were studied in nine nonp olycythemic newborns (gestational age 31-40 wk; birth weight 1680-4000 g; postnatal age 2-28 d) at the end of a prolonged dopamine infusion (3-5 mu g/kg/min i.v, for 2-27 d), Within 2 h after dopamine withdrawa l, GH and PRL levels increased a median 3-fold and 10-fold respectivel y. These data concord to indicate that dopamine is a potent inhibitor of GH and PRL secretion in the human newborn.