ABSTRACT
During the course of each normal menstrual cycle, the human endometrium undergoes a dynamic process of sequential phases of proliferation and differentiation in preparation for implantation. Throughout the reproductive years of a women’s life, this cycle of endometrial growth, differentiation and breakdown is repeated as many as 400 times (Speroff et al., 1999) and reflects the singleness of purpose of the endometrium to create
an environment capable of initiating and subsequently supporting pregnancy. If pregnancy does not occur, the corpus luteum fails resulting in a loss of ovarian steroid support which precipitates a series of biological processes leading to endometrial breakdown. The basic physiology and morphologic changes of menstruation are welldescribed (Noyes et al., 1950; Speroff et al., 1999), however, the precise mechanisms of cellular responsiveness and communication which regulate such extensive but regional tissue destruction remain poorly understood. Normal menstruation represents a highly controlled process initiated by a loss of steroid support and followed by vasoconstriction, tissue collapse, vascular stasis and subsequent healing. Compared to normal menstruation, the highly localized and unpredictable nature of dysfunctional bleeding represents a distinctly different biological entity. Clinically, DUB is defined as excessive bleeding during or between menstrual periods which cannot be attributed to a systemic, anatomical or discreet pathological process. DUB can occur in the presence or absence of the changing steroid environment associated with cyclic ovulation, but this condition is most often associated with anovulation and a hyper-estrogenic environment. Additionally, anovulatory bleeding may occur at any time during the reproductive years of a women’s life, but the peak incidences occur at either the beginning of menstrual life or during the peri-menopause (Schroder, 1954). Numerous clinical strategies may be used for the diagnosis and care of specific patients with dysfunctional bleeding and such information is readily available in recent texts (Speroff et al., 1999). In this chapter, it is not our intention to describe appropriate clinical strategies, rather, we will discuss the local tissue environment of the endometrium at the time of cyclic menstruation in relation to the pathophysiology leading to unpredictable episodes of DUB.
