Growth hormone function in premature and term newborns during the first month of life.

Neonatal somatotropic function is characterized by a discrepancy between el evated growth hormone (GH) levels and low IGF I levels. This study aimed at explaining this discrepancy, particularly to examining if if could result from low GH bioactivity. Serum concentrations of bioactive GH (bio GH), GH measured by radioimmunoassay (riGH), GH binding protein (GHBP), IGF I and I CF binding proteins (IGFBP) rc err determined in 27 premature and term newb orns during the first month of life. Ar day 4, riGH and bio GH concentratio ns were elevated in both premature and term newborns as compared with norma l prepubertal children; GHBP cl,ld IGF I levels were low, with a positive c orrelation with gestational age (P < 0.001). There,ras a positive correlati on between GHBP and ICF I levels. IGFBP-1 and IGFBP-2 levels were elevated and negatively correlated with gestational age (P < 0.005). IGFBP-3 levels were within the range of prepubertal children values and positively correla ted with gestational age (P < 0.005). During the first month, riGH and bio GH levels decreased in all infants, while IGFI levels increased in prematur e infants only, and GHBP levels in term infants only. The elevated levels o f bio GH during the first days of life appear to be related to the low leve ls of IGF I due to a reduced number or function of GH receptors. In prematu re infants the decrease in CN levels observed afterwards appears to be seco ndary to the increase in IGF I levels. In term infants, in the absence of i ncrease in IGFI levels other(s) factor(s) seem(sl to be involved. (C) 1998 Elsevier, Paris.