Secretion and Metabolism of Growth Hormone in Premature and Full-Term Infants1

Abstract

Measurements of plasma growth hormone by radioimmunoassay have been made in umbilical vein plasma of 20 infants at the time of delivery and in peripheral venous blood plasma of 85 normal and 111 premature infants during the 1st months of life. Although a high degree of individual variation was noted, mean levels were high in cord blood at birth and remained high in peripheral vein blood during the first 48 hr. of life (50-72 m[mu]g/ ml). Thereafter, growth hormone concentration fell but remained higher at 8 weeks of life than concentrations measured in adult plasma. The mean plasma growth hormone concentration of premature infants was higher than that of normal infants for much of the period from 2 to 56 days of life. An exaggerated release of growth hormone occurred in response to the induction of hypoglycemia within the first day of life. The disappearance of growth hormone from the plasma of infants is faster than that observed in adult subjects. The induction of hyper-glycemla during the early days of life may stimulate the secretion of growth hormone in full-term infants. Later, the expected inhibition of growth hormone secretion was observed. The high levels of growth hormone encountered in the plasma of infants and the marked alterations which occur with physiological stimuli suggest an important role for this hormone during the early days of life.