these data suggest that a ) the increase in acute anti-ovulatory potency of a synthetic non-estrogenic progestogen over progesterone lies in its ability to reduced selectively serum lh levels at low doses , b ) the progestational block of ovulation takes place via the hypothalamic-pituitary axis and not the ovary , and c ) the retardation of follicular growth that accompanies ovulatory inhibition after diestrous administration of high doses of a progestogen takes place only when both serum fsh and lh are significantly reduced .
C0033308
progesterone
C0033306
progestogen