DISAPPEARANCE RATE OF PROGESTERONE FOLLOWING SIMULTANEOUS REMOVAL OF THE CORPUS LUTEUM AND THE FOETO-PLACENTAL UNIT IN WOMEN

Abstract

ABSTRACT Following simultaneous removal of both the corpus luteum and the foetoplacental unit in the first trimester of human pregnancy, the calculated half life (t½) of endogenous progesterone* in peripheral plasma is dependent on the interval between surgery and the intervals between which the samples are taken. During the first 5 to 6 min after uterotomy the disappearance rate is high and the calculated t½ is 6 min. During the following 5 to 6 min a marked inflection of the slope is observed. The calculated t½ from the second part of the curves is 95 min. When tritiated progesterone is given as iv infusion prior to uterotomy, the disappearance curves for labelled and endogenous progesterone parallel each other. However, when labelled progesterone is given as a single iv injection, the second part of the curves is steeper than when iv infusion is given, i. e. t½ is 43 min. The difference might be explained by assuming a two compartment model of distribution and metabolism. In addition, when a single iv injection of tritiated progesterone is given to an intact pregnant woman and a postmenopausal woman, the second part of the curves is fairly similar, the calculated t½ being 45 and 42 min respectively.