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Question 20. Why are my menstrual cycles irregular?

Posted Apr 28 2010 1:54pm
We often have residents from the Ob Gyn residency program at Georgetown rotating through our office. When they sit in on my consultations they get very familiar with my little song and dance about the normal menstrual cycle. Let's face it....if you don't understand normal reproduction then how can you figure out how to order appropriate tests on your patients to determine the problem. Yet, sometimes in spite of our attempts at education, they still can't figure it out. So here is your chance, dear reader, to become smarter than an Ob Gyn resident! Read on and ask questions as needed....

Here is today's Question of the Day from the upcoming 2nd Edition of 100 Questions and Answers about Infertility!

20. Why are my menstrual cycles irregular?

In a typical reproductive cycle a single follicle (containing a single egg) reaches maturity after 2 weeks culminating with the release of that egg a process called ovulation. Once ovulation has occurred menstrual flow will appear 12-14 days later unless pregnancy supervenes. Thus, most women cycle every 28 days (14 days to grow the egg and 14 days after ovulation until period returns).

Understandably, if a woman has irregular and unpredictable cycles, then logic suggests that she is probably not ovulating normally. Ovulatory problems are usually divided into two main categories: problems with the ovary and problems with the signals from the brain to the ovary. If the irregular cycles result from a lack of follicles within her ovary, then the failure of the ovary to respond will cause the pituitary gland to secrete increased amounts of follicle-stimulating hormone (FSH). Women with elevated levels of FSH are described as having diminished ovarian reserve; if their periods cease entirely, then they are described as having premature ovarian failure (POF). Different laboratories may vary as to how they define an “elevated” level of FSH, so a discussion with your physician is crucial to correctly assess the results of this test. In most cases, however, an FSH level of more than 15 IU/L is evidence of diminished ovarian reserve; FSH levels exceeding 30 IU/L usually signify POF.

If a woman has a normal complement of follicles but still does not have normal cycles, then the problem must lie elsewhere. Most such women suffer from a communication mismatch between the brain and ovary, disrupting the carefully coordinated hormone signals that induce the growth of ovarian follicles. The causes of this disruption can be further classified, with most patients being found to have polycystic ovarian syndrome (see Question 22) as opposed to other hormonal imbalances.
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