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What causes polycystic ovary syndrome (PCOS)?

The exact cause of polycystic ovary syndrome (PCOS) is unclear. However, it involves abnormal levels of a number of hormones, including: luteinizing hormone, male sex hormones, the female sex hormones progesterone and estrogen, and insulin. These hormonal changes can prevent the ovaries from releasing fully mature eggs. Usually, once each menstrual cycle during ovulation, one or more eggs are released from the ovaries into the fallopian tubes. The eggs then pass to the uterus, where, if an egg is fertilized, it can develop into an embryo. In PCOS, eggs are not released, but instead form tiny cysts in the ovaries. Over time, these cysts can build up and the ovaries can become 'polycystic'. Because eggs are less likely to be released from the ovaries, women with PCOS are more likely to have problems with fertility.

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About this article

Author: Dr Joanne Van der Velden PhD, BSc (Hons)
First answered: 18 Sep 2014
Last reviewed: 19 May 2018
Rating: 4.3 out of 5
Votes: 1185 (Click smiley face below to rate)
Category: Endometriosis


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