Ovarian steroid secretion in normally menstruating women II. The contribution of the corpus luteum
Authors: Aedo A.-R. , Pedersen P. H. , Pedersen S. C. , Diczfalusy E. 
Published: December 2008

In 9 normally menstruating women undergoing surgical sterilization by tubal ligation the levels of 12 unconjugated steroids and 4 steroid sulphates 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. In addition, the peripheral levels of progesterone, 20α-dihydroprogesterone, 17-hydroxyprogesterone, oestradiol and oestrone were measured during 3 pre-operative and 3 post-operative days.

The levels of pregnenolone, 17-hydroxypregnenolone, progesterone, 20α-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. Furthermore, compared to the values found in the peripheral blood, the levels of pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, progesterone, 17-hydroxyprogesterone, androstenedione, testosterone and oestradiol were significantly higher in the blood draining both ovaries, whereas 20α-dihydroprogesterone, oestrone and cortisol levels were significantly higher only in the blood draining the 'active' ovary.

Enucleation of the corpus luteum resulted in the following changes:

1) It abolished the previous differences between steroid levels of the blood draining the two ovaries, with the exception of the 20α-dihydroprogesterone levels, which remained elevated in the blood draining the ovary that previously contained the corpus luteum.

2) It diminished the levels of progesterone, 17-hydroxyprogesterone, 20α-dihydroprogesterone, androstenedione, oestradiol and oestrone and increased those of cortisol and pregnenolone sulphate in the blood draining the ovary from which the corpus luteum had been removed.

3) It decreased the peripheral levels of progesterone and oestradiol and increased those of pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, androstenedione, cortisol and pregnenolone sulphate.

4) After the removal of the corpus luteum, the levels of progesterone, 17-hydroxyprogesterone, androstenedione, testosterone and oestradiol remained significantly elevated in the venous blood draining both ovaries when compared to their peripheral levels.

5) The peripheral levels of progesterone, 17-hydroxyprogesterone, oestradiol and oestrone dropped to very low early follicular phase values within 24 h following the removal of the corpus luteum. In contrast, the levels of 20α-dihydroprogesterone reached early follicular phase levels only on the 3rd post-operative day.

It is concluded that the most important steroids secreted by the human corpus luteum are progesterone, 20α-dihydroprogesterone, 17-hydroxyprogesterone, oestradiol and oestrone. Some pregnenolone, 17-hydroxypregnenolone and androstenedione may also be secreted by the corpus luteum. In addition, both ovaries secrete progesterone, 17-hydroxyprogesterone, androstenedione, testosterone, oestradiol and probably also 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 of 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.