Normal and malignant human endometrium express immunohistochemically estrogen receptor alpha (ER-alpha), estrogen receptor beta (ER-beta) and progesterone receptor (PR).

Human endometrium expresses estrogen (ER) and progesterone (PR) receptors, which are related to autocrine and paracrine processes that respond to estrogen and progesterone. The ER and PR expression and distribution pattern may play an important role in endometrial function and pathogenesis. The aim of this study was to evaluate the distribution pattern of ER-alpha, ER-beta and PR in normal (n=15) and malignant (n=11) human endometrial tissue. Commercially available monoclonal antibodies against ER-alpha, ER-beta and PR were used. The distribution of the steroid receptors was evaluated using the IRS-score and the Mann-Whitney rank-sum test was used to compare the means. Correlation was assessed with the Spearman factor and linear regression analysis. ER-alpha, ER-beta and PR declined significantly (p <0.05) in normal glandular epithelium from proliferative to late secretory phase, although the staining intensity of ER-beta was lower than that of ER-alpha. ER-alpha, ER-beta and PR were also expressed in malignant endometrial tissue. A significant correlation by regression analysis of ER-alpha and ER-beta was demonstrated, showing a dependence in the expression of these steroid receptors. The ER-alpha/ER-beta ratio decreased significantly from normal to malignant endometrial tissue (p<0.05), while the ER-beta/ER-alpha ratio showed statistical differences within normal endometrial tissue. These results showed the presence of steroid receptors in normal and malignant human endometrium, indicating a significant role in endometrial physiology and malignant transformation.