Endometrial Determinism of Endometriosis: An Unnecessary Adjunct to Retrograde Menstruation

The observation that retrograde menstruation is almost universal while only a small proportion of women suffer with endometriosis is among the most quoted challenges to Sampson’s hypothesis. Addressing this challenge has focused on identifying unique features in the endometrium of affected women. The assumption that endometriosis develops from an aberrant endometrium forms the cornerstone of “endometrial determinism.” This review appraises the evidence for endometrial aberrations starting with an appraisal of retrograde menstruation. The quantity of endometrial tissue in retrograde menstruation is not well defined and is probably small, variable and its characteristics remain largely unknown. There are well documented differences between the eutopic endometrium in the presence and absence of endometriosis. On the other hand, at least some of the endometrial aberrations in endometriosis are the result of the disease and similar “defects” have been identified in the absence of endometriosis. The evidence provided here challenges endometrial determinism as the primum movens in endometriosis. Indeed, it is unclear that the theory is a necessary adjunct to Sampson’s hypothesis. Further research is needed that can further our understanding of the natural history or endometriosis and that can enable the development of novel theories of its pathogenesis.