[Changes in steroid enzyme activity in the human endometrium during the menstrual cycle]

Sulfokinase, sulfatase, 17 beta-HSD, 20 alpha-HSD, 3 beta-HSD and 5 alpha-reductase activity and steroid concentrations including estradiol, estrone, estrone-sulfate, progesterone, 20 alpha-dihydroprogesterone, DHA and DHA-sulfate in endometrial tissue were examined in order to study the changes in steroid metabolism in relation to the menstrual cycle in the human endometrium. Thirty-one (14) proliferative and 17 secretory) endometrial tissue samples were obtained from women who underwent hysterectomy. Low enzymatic activity of sulfokinase, sulfatase and 17 beta-HSD activity were observed in the proliferative phase (0.25, 8.5, 3.1 nmole/mg protein/h). A pronounced increase in enzymatic activity was observed in the early secretory phase and activity gradually decreased toward the mid and late secretory phase. On the other hand, 20 alpha-HSD and 3 beta-HSD activity did not change during the cycle. 5 alpha-reductase activity was not detectable under the conditions used. The concentration of progesterone in the secretory phase was significantly higher than that in the proliferative phase. The concentration of estradiol in the proliferative phase was significantly higher than that in the secretory phase. There was no significant change in the concentration of estrone, estronesulfate, 20 alpha-dihydroprogesterone, DHA or DHA-sulfate during the cycle. The relationship between the steroid concentration and the enzymatic activity was discussed. The results suggested an active role of the endometrium in controlling the biological effect of steroids.