Why don't I have a period?

I am 18 years old and a virgin. I got my first period when I was 13 and they were very regular for a few years. Until I turned 15. My period disappeared for 8 months. When I finally went to the doctor to find out what was going on, they ran blood and urine tests. There was nothing wrong that they could detect, so they decided to put me on birth control to try to force me to have a period again. This worked very well. For three months I took the birth control and my period came right on time. After that I got off the birth control, and my period continued to be pretty regular. Now over the last 8 months I've noticed that they're starting to get very irregular again. I'll skip one or two, but it will always show back up unexpectedly. But right now, I'm waiting for my period to reappear after another absence. It has been 3 months since I had a period and I'm starting to get a little worried that it's pulling another disappearing act. I'm really not happy with how irregular my periods are, but I don't want to have to live on birth control. And I'm also concerned for what could be the cause. Can you tell me what might be going on to cause this irregular and sometimes complete lack of a menstrual cycle?

[Elaine Brown, MD]

Hi!
Your irregular periods are most likely due to a variant of polycystic ovary syndrome (PCOS).  If you are not ready for pregnancy, then usually the best way to treat this problem is with oral contraceptives.  Some women prefer to take progesterone on a moth ly basis.  The problem is that there tends to be build up of tissue within the uterine lining if there are too few periods, and over years and years, this can lead to problems such as hyperplasia or even cancer.  Often women need some medication to conceive too, but absence of periods should not be interpreted as a form of birth control.
I usually test my patients' thyroid values, their prolactin levels, and their am 17 oh progesterone levels before classifying them as PCOS patients.
Good luck!
Dr B