Polycystic ovary syndrome signs and symptoms often begin soon after a woman first begins having periods (menarche). In some cases, PCOS develops later during the reproductive years, for instance, in response to substantial weight gain.
It is important to first understand the normal menstrual cycle. The normal menstrual cycle contains two hormones, progesterone and estrogen, which are made by the ovaries. Each month these hormones cause the endometrium to grow in preparation for a possible pregnancy. About 12-14 days before the start of a period, an egg is released from the ovary. This is called ovulation. The egg travels down the fallopian tubes where it can be fertilized by sperm. If it is not and pregnancy does not occur, the levels of hormones decrease and signal the uterus to shed its lining. This shedding is the menstrual period. In most women, this cycle lasts about 28 days but cycles that are 7 days shorter or longer are considered normal.
This is the most common characteristic of PCOS. Examples include menstrual intervals longer than 35 days; fewer than eight menstrual cycles a year; failure to menstruate for four months or longer; and prolonged periods that may be scant or heavy.
Although some women with PCOS have regular periods, high levels of androgens (‘male’ hormones) and excess insulin can disrupt the monthly cycle of ovulation and menstruation.
If you have PCOS, your periods may be ‘irregular’ or stop altogether. The average menstrual cycle is 28 days with one ovulation when eggs are released, but anywhere between 21 and 35 days is considered ‘normal’. An ‘irregular’ period cycle is defined as either:
- Eight or less menstrual cycles per year
- Menstrual cycles longer than 35 days
- Some women with PCOS also experience heavier or lighter bleeding during their menstrual cycle.