There are a few conditions that can cause unwanted hair growth in women (hirsuitism). Polycystic Ovarian Syndrome (PCOS) is the most common, affecting 8-10% of women. Hair growth in the midline of the body (such as the upper lip, chin, lower stomach, or your back) can be due to PCOS. Weight gain can make PCOS symptoms worse. We diagnose PCOS with blood tests and a sonogram, and treatments can reduce the hair growth. Other conditions that can cause unwanted hair growth include adrenal gland disorders.