**2. Endometrial phenotypes in endometriosis**

The interest for diagnosis and therapeutic success connected to side effects, limitations and failure rate of different classes of medication, and high risks of recurrence after surgery or medication discontinuation imposed the analysis of endometrium phenotypes, proliferative and differention *in vitro* capacities of stromal cells from ectopic lesions of peritoneum, ovaries, and deeply infiltrating endometriosis in comparison to the same structures of normal women, using the new techniques as contrast microscopy, immunocytochemistry, functional bioassays [27] and RT- qPCR of endometrial genes.

The study of Burney et al. [28] analyzed eutopic and ectopic endometria comparative to non ill women, and it was demonstrated a molecular phenotype of attenuated progesterone response within eutopic endometrium, from the dysregulation of numerous genes which are progesterone regulated, and the progesterone resistant phenotype is more frecquent in ectopic endometrium comparative to non-ill cases. This condition is associated to a pro-inflammatory phenotype [29, 30] which increases both estrogen dominance, and progesterone resistance. The eutopic endometrium of ill women has an attenuate response to P4 because estrogenresponsive genes are not suppressed in their stromal cells in early secretory phase of menstrual cycle comparative to normal [28, 31, 32]. The British and Italian doctors' conclusion [29] was that endometriotic cell lines, and stromal eutopic endometrial cells in ill-women are lossing the capacities of differentiation, and respectively of deciadualisation, aspects that explain cells capacities for proliferation and survival in the ectopic environment, and high infertility/subfertility rates. Deep endometriosis appears to be a special type, because predominance of PR less active isoform (PR-A) over the full length, due to epigenetic abnormalities affecting PR gene transcription, associated to oxidative stress, facts that induce a condition of more resistant to size regression upon medical treatments [7].
