Precursors of Urinary Pregnanediol and Their Influence on the Determination of the Secretory Rate of Progesterone

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Abstract
In an attempt to measure the secretory rate of pregnenolone and progesterone, 3H-labeled pregnenolone and 14C-labeled progesterone were administered intravenously to various normal individuals. The results indicate that pregnenolone (and/or possibly pregnenolone sulfate) is secreted in significant amounts and that this compound may contribute in a quantitatively important manner to the urinary level of pregnanediol. As a consequence of this contribution, the secretory rate of progesterone cannot be estimated from the specific activity of urinary pregnanediol following administration of labeled progesterone alone. Moreover, the results also demonstrate that, even if both labeled progesterone and pregnenolone are injected, the secretory rate of neither progesterone nor pregnenolone can be determined.