Ovarian steroid secretion in normally menstruating women II. The contribution of the corpus luteum

Abstract

In 9 normally menstruating women undergoing surgical sterilization by tubal ligation, the levels of 12 unconjugated steroids and 4 steroid sulfates were analyzed in the peripheral circulation and in the venous blood draining both ovaries before and after the surgical removal of a freshly formed corpus luteum. The peripheral levels of progesterone, 20.alpha.-dihydroprogesterone, 17-hydroxyprogesterone, estradiol and estrone were measured during 3 preoperative and 3 postoperative days. The levels of pregnenolone, 17-hydroxypregnenolone, progesterone, 20.alpha.-dihydroprogesterone and cortisol were significantly higher in the venous blood draining the active ovary (containing the corpus luteum) than in the blood draining the contralateral inactive ovary. Compared to the values found in the peripheral blood, the levels of pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, progesterone, 17-hydroxyprogesterone, androstenedione, testosterone and estradiol were significantly higher in the blood draining both ovaries. 20.alpha.-Dihydroprogesterone, estrone and cortisol levels were significantly higher only in the blood draining the active ovary. Enucleation of the corpus luteum abolished the previous differences between steroid levels of the blood draining the 2 ovaries, with the exception of the 20.alpha.-dihydroprogesterone levels, which remained elevated in the blood draining the ovary that previously contained the corpus luteum. The enucleation also resulted in diminished levels of progesterone, 17-hydroxyprogesterone, 20.alpha.-dihydroprogesterone, androstenedione, estradiol and estrone and increased cortisol and pregnenolone sulfate levels in the blood draining the ovary from which the corpus luteum had been removed. The peripheral levels of progesterone and estradiol decreased and those of pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, androstenedione, cortisol and pregnenolone sulfate increased. After the removal of the corpus luteum, the levels of progesterone, 17-hydroxyprogesterone, androstenedione, testosterone and estradiol remained significantly elevated in the venous blood draining both ovaries when compared to their peripheral levels. The peripheral levels of progesterone, 17-hydroxyprogesterone, estradiol and estrone dropped to very low early-follicular phase values within 24 h following the removal of the corpus luteum. The levels of 20.alpha.-dihydroprogesterone reached early follicular phase levels only on the 3rd postoperative day. The most important steroids secreted by the human corpus luteum are progesterone, 20.alpha.-dihydroprogesterone, 17-hydroxyprogesterone, estradiol and estrone. Some pregnenolone, 17-hydroxypregnenolone and androstenedione may also be secreted by the corpus luteum. Both ovaries secrete progesterone, 17-hydroxyprogesterone, androstenedione, testosterone, estradiol and probably pregnenolone, 17-hydroxypregnenolone and dehydroepiandrosterone. The surgical stress associated with the laparotomy resulted in elevated plasma levels of a number of adrenal steroids, many of which are normally also produced by the ovaries. The presence of these steroids and their ovarian metabolites in the venous blood draining the ovaries imposes major limitations on the interpretation of results obtained in short-term studies, unless complemented with the long-term assessment of the peripheral steroid levels.