Concentrations of prostaglandins F2alpha and E2 in the endometrium throughout the human menstrual cycle, after the administration of clomiphene or an oestrogen-progestogen pill and in early pregnancy

Abstract

The concentrations of prostaglandins F2alpha (PGF) and E2 (PGE) were measured by gas chromatography-mass spectrometry in endometrial tissue obtained from 45 normal women at various stages of the menstrual cycle. During the proliferative stages, the concentration of PGF in the endometrium was correlated with the concentration of oestradiol in the plasma. The concentration of PGF during the mid-secretory stage (mean, 2.047, range, 0.549-4.344 microgram/g fresh endometrial tissue) was significantly higher than the concentrations during the late proliferative and late secretory stages. The endometrial concentration of PGE did not show a cyclic variation. The concentrations of PGF and PGE in samples of endometrium collected after the administration of clomiphene were significantly lower than the concentrations observed in endometrial tissue obtained from normally menstruating women in the mid-proliferative period. The administration of an oestrogen-progestogen pill resulted in higher endometrial concentrations of PGE than were measured in the mid-secretory phase. The concentrations of PGF and PGE in decidual tissue (conceptual age 3-10 weeks) were lower than those measured at any stage of the normal menstrual cycle. During the human menstrual cycle, high levels of oestradiol and progesterone are related to high endometrial levels of PGF but not PGE. The presence of a conceptus apparently blocks the effect of high concentrations of ovarian steroids on the synthesis or catabolism of prostaglandins.