Comparison of urinary 6β-hydroxycortisol/cortisol ratio between neonates and their mothers

Abstract

Aims. To assess CYP3A enzyme activity in human neonates by measuring the urinary 6β-hydroxycortisol/cortisol (6β-OHF/C) ratio. Methods. Fifty-six mature male neonates with normal delivery, seventeen of their mothers and twenty-four healthy non-pregnant young women participated in this study. Urinary 6β-OHF/C ratio was determined on the day of birth in neonates and their mothers. In addition, changes in the ratio after birth were determined in neonates. Results. On the day of birth, the urinary 6β-OHF/C ratio of neonates was significantly higher than that of their mothers (20.5 vs 6.9). In contrast, no significant difference was observed in the mean ratio of urinary 6β-OHF/C between women with and without pregnancy (6.9 vs 9.0). The urinary 6β-OHF/C ratio after birth was decreased day by day in neonates. Conclusion. These results indicate that the high urinary 6β-OHF/C ratio in mature neonates on the day of birth is independent of the activity of CYP3A enzyme in their mothers.