What are the common causes of pcos?

Not known: It is not known what triggers pcos. Something at molecular and genetic level triggers the cascade of ovarian and hormonal changes. That in turn effects the entire body.

Obesity: The predominent theory as to the cause for pcos is the elevated estrogen levels that occur as a result of obesity. While some women with pcos are not overweight - the vast majority are - and most of them will experience resolution of the pcos simply with weight loss.