ADRENOCORTICAL STEROID METABOLISM IN NEWBORN INFANTS. II. URINARY EXCRETION OF 6β-HYDROXYCORTISOL AND OTHER POLAR METABOLITES*†

Studies of corticosteroids in the urine of normal newborn infants were performed on the free and glucuronide fractions after each was extracted by means of methylene dichloride and ethyl acetate. The latter organic solvent was found to be essential for efficient extraction of the polar metabolites of cortisol. From this fraction, 6β-hydroxycortisol was isolated and identified. The data obtained after cortisol loading suggested that the very polar metabolites are more important pathways of cortisol disposition in the newborn infant than they are later in life. The studies also showed that in spite of the high percentage of the urinary steroids extractable before hydrolysis from the urine of the newborn infant, cortisol itself is present only in very small amounts. It appears, therefore, that the normal infant metabolizes cortisol efficiently, but that degradation pathways of minor quantitative importance in the adult are more extensively used during the first postnatal week.