Physiological Disposition of 4-C14-Cortisol During Late Pregnancy1

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Abstract
The metabolism of 4-C14-cortisol during late pregnancy, was markedly altered. In plasma, the half-life of free radioactivity was twice that in control subjects and the amount of radioactivity released by B-glucuronidase hydrolysis was smaller than normal. The total amount of urinary radioactivity excreted was diminished, with an increase in the "free fraction" and a decrease in the "glucuronoside fraction". Data suggest that the increase in plasma-free 17-hydroxycorticosteroitis observed near term is related to a slower catabolism of cortisol rather than to a more rapid rate of its production. In cord plasma, the amounts of free radioactivity and that released by B-glucuronidase hydrolysis were 0.5-0.2 those of the corresponding mother; the total amount of radioactive steroid crossing the placenta appeared to represent 2-3% of the dose administered to the mother.