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While the normal menstrual cycle in the human typically lasts 4 weeks (28 days, range 21-35 days) and consists of a follicular phase , ovulation, and a luteal phase , followed either menstruation or pregnancy, the anovulatory cycle has cycle lenghts of varying degrees. In many circumstances, menstrual intervals are prolonged exceeding 35 days leading to oligomenorrhea (cycle >35- 180 days interval), or even longer, amenorrhea. In other cases, menstruation may be fairly regular (eumenorrhea ), or more frequent (intervals < 21 days), or there may be a loss of menstral pattern (menorrhagia, dysfunctional uterine bleeding).
Estrogen Breakthrough Bleeding
Menstrual bleeding in the ovulatory cycle is understood as a result of a decline in progesterone due to the demise of the corpus luteum. It is thus a progesterone withdrawal bleeding. As there is no progesterone in the anovulatory cycle bleeding is caused by the inability of estrogen - that needs to be present to stimulate the endometrium in the first place - to support a growing endometrium. Anovulatory blleding is hence termed estrogen breakthrough bleeding.
A physician needs to investigate for possible causes of anovulation. Common causes are:
- Polycystic ovary syndrome
- Hypothalamic dysfunction
- Ovulatory dysfunction
- Thyroid disorders
With excessive or prolonged bleeding the diagnosis has to be made by a physician on a speedy basis. Exluded need to be other causes of gynecological bleeding , specifically bleeding related to pregnancy, leiomyoma, and cancer of the cervix or uterus.
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