METABOLISM OF FETAL AND NEONATAL ADRENAL-STEROIDS

There are marked differences between metabolism of steroids by the human fetus, neonatal infant and adult. These have been assessed by examination of the steroid excretion patterns in the fetus using analysis of pregnancy urine from patients with placental sulphatase deficiency and amniotic fluid from normal pregnancy, and in the neonate by analysis of urine collected during the first days of life. Metabolites of corticosterone and aldosterone have also been measured in infants with hyper-secretion of these hormones. The major differences in the perinatal period in comparison with adulthood are: (1) 3β-hydroxy-5-ene steroids are excreted in much greater absolute and relative amounts; (2) all the 3β-hydroxy-5-ene steroids contain additional hydroxyl groups in the 16α, 18 or 21 positions; (3) of the metabolites of cortisol and corticosterone, 60% contain additional hydroxyl groups in the 1β- or 6α-position, compared with 2-5% in adults; (4) more than 90% of the corticosteroid metabolites contain an 11-oxo group; (5) 21-dehydroxylation of corticosterone metabolites by gut bacteria is absent. Aldosterone metabolism does not differ greatly at different stages of life. The patterns of steroid conjugation are also similar with predominantly glucuronide conjugation of corticosteroids and sulphation of 3β-hydroxy-5-ene steroids. However, a significant proportion of the more polar corticosteroid metabolites are excreted by infants as free compounds. Adrenal steroid output decreases dramatically post partum. Other changes include a relative increase of 15- and 18-hydroxylation of 3β-hydroxy-5-ene steroids and an apparent decrease of 21-hydroxylation, the latter possibly due to utilisation for miner-alocorticoid biosynthesis. Following progressive changes, the adult pattern of steroid metabolism is reached at about 1 year of age. © 1979.