Anovulatory Cycle

Abstract

Most ovulatory menstrual cycles last between 21 days and 35 days. The duration of normal menstrual flow is generally 5 days, with most blood loss occurring within the first 3 days (4). The median age of menarche is 12.43 years with a typical cycle range of 21–45 days, with 7 or fewer days of blood flow in younger females (4). Ovulatory cycles are predictable, but in most women, the length of the cycle can vary by a few days each month. Overall, the length of the menstrual cycle remains rela-tively constant throughout the reproductive years, but cycle length varies as a woman approaches menopause (5). Menstruation results from a complex interaction between the hypothalamus, the anterior pituitary gland, the ovary, and the endometrium. The selection and ovu-lation of a mature oocyte is the result of the coordinated process that results in the cyclic growth and differentia-tion of the endometrium. Dysfunction at any level can interfere with ovulation and prevent normal develop-ment and sequential shedding of the uterine lining. During a normal ovulatory cycle—including fol-licular development, ovulation, corpus luteum develop-ment, and luteolysis—the endometrium is sequentially exposed to ovarian production of estrogen alone, fol-lowed by a combination of estrogen and progesterone. At the end of the cycle, estrogen and progesterone with-drawal occurs. Follicle development and ovulation are associated with a cyclic pattern of endometrial histology commencing with proliferation followed by secretory change, shedding, and repair. Normal ovarian steroid production is important for nidation and pregnancy. From a clinical perspective, the result is cyclic, predict-able, and relatively consistent menstrual blood loss (6). An intact coagulation pathway is important in regu-lating menstruation. Menstruation disrupts blood vessels, but with normal hemostasis, the injured blood vessels are rapidly repaired. Restoration of blood vessels requires successful interaction of platelets and clotting factors. Medications, such as warfarin, aspirin, and clopidogrel, can impair the coagulation system and be associated with heavy bleeding.