Dear An: The most common reason for a menstrual pattern like you have described is not having an ovulation every month. In a normal cycle, estrogen is produced all month. Estrogen is responsible for building up the lining of your uterus so you have something to shed each month. The good news is that you have enough estrogen to make a lining that does shed--although you are entering perimenopause (the four to five years before final period).
In a normal cycle, progesterone production increases following ovulation and release of an egg.. Progesterone "stabilizes" the uterine lining in preparation for a possible implantation of a new pregnancy. If you are not pregnant that month the levels of estrogen and progesterone fall, triggering the release of the uterine lining—your period. So, if you do not ovulate, the estrogen build up of the lining continues, but without the usual ovulation associated progesterone. Thus, the hormone levels don't decline, and the lining stays up inside the uterus—as either a missed period or the too thick lining will begin to shed erratically under its own weight..
There are many causes for not ovulating: low thyroid, pituitary problems, ovarian cysts, physical stressors (eg sudden increases in exercise, crash dieting), emotional stressors (problems with parents or partners, finances), increased body weight, anorexia, rotating shifts at work, etc. In your specific case, your age and probably being perimenopausal, can interfere with ovulations.
The greatest concern would be that a too thick uterine lining can develop abnormal cells. If your cycle does not return to normal see your GYN or local family planning clinic. They may decide to take a sample of uterine lining ("endometrial biopsy") to look for abnormal cells or even polyps of the lining. Sometimes an ultrasound is suggested to see if the lining looks too thick or if a large polyp, fibroid, or ovarian cyst is visible--all of these can prompt bleeding between periods.
Yes, it could be that your transition into menopause is starting. Pretty much anything goes during perimenopause - more or less frequent periods, heavier bleeding, lighter bleeding, shorter periods, longer periods - no predictability. This is all due to wildly fluctuating hormones. For some it is more extreme than others.
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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