Growth hormone (hGH), insulin-like growth factor-I (IGF-I) and prolactin (PRL) were measured in the cord and venous blood of small for gestational age (SGA) neonates in order to evaluate their endocrine status during the first 3 days of life. Although there were SGA newborns with both high and normal levels of hGH, the mean (+/- SD) concentration of hGH in the cord blood of the SGA neonates was 72.1 +/- 50.6 ng/ml, whereas in the appropriate for gestational age (AGA) newborns it was 37.0 +/- 23.5 (p = 0.001). The IGF-I in the cord blood of the SGA and the AGA newborns was 194.2 +/- 174.8 ng/ml and 77.3 +/- 50.2, respectively (p = 0.013). The PRL in the SGA and AGA newborns was 184.8 +/- 62.4 ng/ml and 126.8 +/- 60.5, respectively (p = 0.0005). On the 3rd day the hGH in the SGA babies was 50.7 +/- 41.2, whereas in the AGA it was 24.3 +/- 12.3 (p = 0.034). On the same day the IGF-I was 133.9 +/- 120.9 and 44.8 +/- 31.6, respectively (p > 0.05). Similarly, the PRL was 157.1 +/- 52.3 and 90.9 +/- 52.5, respectively (p = 0.0008). All neonates with high hGH concentrations had low IGF-I levels, whereas of those with normal hGH half had high and half normal IGF-I levels. There was no difference in the hormone levels between symmetric and asymmetric intrauterine growth-retarded infants. The findings suggest that the SGA neonates are heterogeneous comprising three groups.(ABSTRACT TRUNCATED AT 250 WORDS)