SERUM CONCENTRATIONS OF CORTISONE AND CORTISOL IN PREMATURE-INFANTS

To determine the relationship between biological active cortisol and i ts inert metabolite cortisone accurately in premature infants, serum c ortisone and cortisol concentrations were measured by reversed-phase h igh-performance liquid chromatography (HPLC) in a group of 232 prematu re infants and in a control group of 127 children and 88 adults. In th e control group, serum cortisone concentrations were greater than seru m cortisol levels during the first 2 months after birth; cortisol leve ls were higher than cortisone levels after 2 months of age. However, i n premature infants, serum cortisone concentrations were greater than serum cortisol revels even after the first 2 months, and total concent rations of cortisone and cortisol were equal to those in controls. Res ults were then analyzed according to the equivalent gestational age of premature infants. Cortisone was predominant in premature infants old er than 32 weeks of equivalent gestational age, but cortisol was highe r than cortisone from equivalent gestational age 24 to 31 weeks. These findings suggest that the ability of premature infants to secrete glu cocorticoids resembled that of normal controls. Also, the fetal zone o f the cortex, which is associated with a predominance of cortisone, re mained functional in premature infants for a longer time than in contr ol infants, Our findings that in premature infants cortisone was predo minant compared with cortisol and the sum of cortisone and cortisol wa s equal to that in the controls indicate that cortisone cannot be disr egarded whenever the cortisol revel is estimated, although cortisone i tself is recognized to be biologically inactive. Simultaneous measurem ent of serum cortisone and cortisol concentrations is important when a drenocortical function is being determined, especially in premature in fants. Copyright (C) 1997 by W.B. Saunders Company.