Comparison of cellular levels of steroid receptors in uterine leiomyoma and myometrium.

To support the estrogen hypothesis in the pathogenesis of leiomyoma, total cellular estrogen receptor (ER) levels (the sum of levels in cytosol and nuclear KCl-extractable and nuclear non-KCl-extractable fractions) were assayed and compared with levels of progestin (PR) and androgen (AR) receptors in the leiomyoma and the corresponding myometrium. The ratios of ER to PR or AR levels were higher (with statistical significance) in leiomyoma than in the corresponding normal myometrium, both in terms of total cellular levels in each individual case and nuclear levels. It appears that estrogen sensitivity is higher in the leiomyoma than in the corresponding myometrium, due to the relative increase in ER.