Endometriosis: Oestrogen and progesterone receptors in endometriotic tissue and endometrium: comparison of different cycle phases and ages*

The levels of oestrogen and progesterone receptors were analysed in 62 endometriotic tissue samples obtained at laparotomy of 58 women and in samples of endometrium obtained simultaneously from 49 of the women. Both ligand techniques and enzyme immunoassays were used for the assays. The steroid receptor levels were significantly lower in endometriotic tissue than in endometrium, both in cytosol and nuclear fractions. The differences were most pronounced in follicular phase. In endometrium the oestrogen and progesterone receptor levels varied during the menstrual cycle, being highest in follicular phase. In endometriotic tissue, the oestrogen receptor level remained low throughout the cycle. The progesterone receptor level, determined by immunoassay, increased during the menstrual cycle, being higher in luteal than in follicular phase. This cycle phase pattern was found neither in the nuclear progesterone receptor level nor when the cytosol was assayed with the ligand technique. In contrast to endometrium, there were no correlations between patients' age and steroid receptor levels in endometriotic tissue. The results show that oestrogen and progesterone receptors in endometriotic tissue have a different pattern during the menstrual cycle than endometrium and that the progesterone receptors synthesized are not all biologically active. These results strengthen previous data indicating differences in the hormonal regulation of the two tissue types.