One study of five premature infants, not exposed to antenatal steroids(ANS), has demonstrated that cortisol (F) is secreted in discrete bursts at approx. 80 min. intervals (Metzger JCEM 1993). The aim of this study was to assess the effect of ANS on cortisol secretion in neonates < 33 weeks gest. age. Blood samples for plasma F determination were taken via indwelling arterial lines at 15 min. intervals for six hours. Neonates were studied in the first 7 postnatal days. Characteristics of F secretion were estimated by deconvolution analysis. Deconvolution parameters in five neonates (median g.a. 29 wks, b.wt. 1200 gm) where the ANS-study interval was < 7 days (Steroid Gp) were compared with 11 neonates (median g.a. 30 wks, b.wt. 1450 gm) who received no or remote ANS (No/Remote Steriod Gp). Pulsatile F secretion was observed in all infants. Data in the Table are given as median and inter-quartile range. The F secretory burst half-duration, interburst interval, and number of bursts per 6h were similar for No/Remote and Steroid Gps; 21.0 vs 21.4 mins, 64.8 vs 65.6 mins, and 5 vs 6 bursts, respectively. This study confirms that in premature infants cortisol is secreted in pulses and that neonates recently exposed to ANS also display pulsatile secretion. Neonates exposed to ANS < 7 day prior to being studied had a significantly lower mass of F secreted per burst. Deconvolution analysis incorporating larger numbers of study patients may further delineate characteristics of F secretion and clearance in the premature neonate.

Table 1
Full size table