The uterine endometrium of placental mammals in general and human in particular is a highly dynamic, proliferative and regenerative tissue. It undergoes cycles of growth and regression during each menstrual cycle with a growing capacity from 0.5-1mm in the proliferative phase to 5-7 mm during the secretory (leutal) phase. These phases are characterized by cyclic processes of cellular proliferation, differentiation and shedding. Recent studies have revealed that the endometrium harbours a large population of mesenchymal stromal cells. There are several reports indicating the homing of bone marrow stem cells and endothelial progenitor cells in regenerating endometrium. However, it is not clear whether endometrial cells mobilise to participate in the repair and regeneration of vital organs/tissues. We hypothesize that a very small percentage of the endometrial cells may set in circulation during menstrual cycle to facilitate endogenous regeneration of vital organs in the body. These cyclical events may be responsible for providing a protective barrier to women during her child-bearing age. Disappearance of this barrier after menopause probably makes her vulnerable for post menopausal symptoms. There is a circumstantial evidence to vouch for the presence of circulating stem/progenitor cells in peripheral blood which are likely to lodge in injured organs for their possible repair. As the endometrium harbors a large population of mesenchymal stromal cells, it is possible that retention of the uterus through secretion of reparative/growth promoting factors, may provide legitimate stem cells to enter circulation and "set up shop" in other tissues like bone marrow stem cells. In this context we propose uterus to be the culprit for the postmenopausal syndrome.