Prolonged steroidogenesis in luteinized ovaries of hypophysectomized rats

Luteinized ovaries of rats hypophysectomized shortly after ovulation 25-80 days previously secrete considerable amounts of 20 alpha-dihydroprogesterone (20 alpha-hydroxy-4-pregnen-3-one, 20 alpha-OHP) into the bloodstream. The serum concentration of 20 alpha-OHP in these hypophysectomized animals is almost similar to that of progesterone in intact pseudopregnant rats on day 7 of pseudopregnancy, in spite of the absence of demonstrable amounts of prolactin. Isolated corpora lutea of the last generation and the remainder of the ovarian tissue both contained 20 alpha-OHP. Six months after hypophysectomy no detectable amount of 20 alpha-OHP was found in the serum. Androgenized rats, devoid of corpora lutea, did not produce 20 alpha-OHP after hypophysectomy. These data show that pituitary hormones are not required for the prolonged synthesis and secretion of 20 alpha-OHP by the luteinized ovary.