WebMD Answers
The cause of polycystic ovary syndrome (PCOS) is not fully understood, but genetics may be a factor. If you have PCOS, your sisters and daughters have a 50% chance of developing PCOS.1
The first signs of PCOS are usually after a girl's menstrual cycle begins (menarche). A teen with menstrual periods over 45 days apart may need to be seen by a doctor to make sure she doesn't have PCOS. (Normally, the first periods and ovulation are hard to predict. They become regular within the first 2 years after menarche. For more information, see the topic Normal Menstrual Cycle.) In some women, PCOS starts after a big weight gain.2, 3
PCOS problems are caused by hormone changes. One hormone change triggers another, which changes another. This makes a "vicious circle" of out-of-balance hormones in your endocrine system, including:
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