Determination of Estradiol, Estrone, and Progesterone in Serum and Myometrium: Correlation with the Content of Sex Steroid Receptors and 17β-Hydroxysteroid Dehydrogenase Activity throughout the Menstrual Cycle

Abstract

A study has been carried out to compare the influence of estradiol, estrone, and progesterone on the cytoplasmic estradiol and progesterone receptor levels and 17β-hydroxysteroid dehydrogenase (17β-HSD) activity in human myometrium. The steroid hormone concentrations were measured simultaneously in both serum and cytosol of myometrial tissue. The estradiol receptor levels were highest during the midproliferative phase. The highest progesterone-binding capacity was found in myometrial cytosol around ovulation. The midcycle peak of the cytoplasmic progesterone receptor level correlated well with the first peak of tissue concentrations of estradiol and the increase of progesterone tissue concentrations. During the luteal phase, in contrast to the follicular phase, the progesterone receptor level decreased, whereas serum progesterone concentrations were high. The midcycle peak of cytoplasmic progester one-binding capacity and the increase of progesterone tissue levels at the same time were followed by an activation of 17β-HSD. The myometrial concentration of this enzyme, which converts estradiol to estrone, was approximately 10-fold higher during the early secretory phase than during the proliferative phase. In contrast to serum, estrone levels were higher in cytosol of myometrium during the luteal phase than during the follicular phase. The maximum 17β-HSD activity after midcycle was followed within 3 days by the highest estrone tissue concentrations. Thereafter, both estrone tissue levels and 17β-HSD activity decreased continuously in a similar manner until menstruation. The second maximum of estradiol serum concentrations during the midsecretory phase was not found in myometrium.