Comparison of plasma and myometrial tissue concentrations of estradiol-17 beta and progesterone in nonpregnant women.

Plasma and myometrial tissue concentrations of estradiol (E2) and progesterone (P) were measured by radioimmunoassay techniques in samples obtained from women with regular menstrual cycles and from women in pre- or postmenopausal age. In women with regular cycles, the tissue concentration of E2 ranged from 0.13 to 1.06 ng/g wet weight, with significantly higher levels around ovulation than in follicular or luteal phases of the cycle. The tissue concentration of P ranged from 2.06 to 14.85 ng/g wet weight with significantly higher level in luteal phase than in follicular phase. The tissue/plasma ratio of E2 ranged from 1.45 to 20.36 with very high values in early follicular phase and the lowest in mid-luteal phase. The ratio for P ranged from 0.54 to 23.7 and was significantly lower in the luteal phase than in other phases of the cycle. One woman in premenopausal age with an ovarian cyst was the only case with a tissue/plasma ratio of E2 Less Than 1, since her plasma E2 levels were exceptionally high. In postmenopausal women, the tissue concentration of E2 was not significantly lower than in menstruating women in follicular phase, and the tissue concentration of P was not significantly lower than in fertile women in any of the phases. Neither in these women nor in menstruating women was there a close correlation between tissue and plasma levels. The present data indicate that the myometrial uptake capacity for ovarian steroids may be saturated, and also that a certain amount of these steroids is bound to tissue even if plasma levels are low.