Why do i have polycystic ovary syndrome when i'm really thin?

Probably genetic: Not all women with polycystic ovarian syndrome (pcos) are overweight or obese. Some pcos women are thin, some have regular cycles, some have irregular or no periods. Some have symptoms, some don't. You probably have a genetic predisposition to pcos, which can run in families. We haven't identified the exact genes yet. You still have increased risk of Insulin resistance/ pre-diabetes even if thin.

50% are thin: Pcos splits 50/50 into 'thin' and excess weight ; patients are similar but not identical. The confusion is understanding differences in diagnostic criteria vs. Other features of pcos. Most experts diagnose pcos as 2 out of 3: irregular or missed periods, clinical or blood evidence of extra androgens, and polycystic look of ovaries on ultrasound. Weight, hair-growth, are associated but variable.