This is a hormone imbalance that can result in irregular periods, unwanted hair growth, acne, extra weight gain, baldness, and patches of dark skin on the back of your neck and inner thighs that weren't caused by some guy giving you a hickey.
Nearly 1 of every 10 to 20 women have PCOS, and it tends to be especially common in young women. Cases can be mild or severe. Researchers still don't know what causes it, but they suspect that insulin resistance plays a factor in many cases.
The symptoms of PCOS start when your pituitary makes too much leutinizing hormone (LH) and/or your pancreas makes too much insulin. This causes your ovaries to make more testosterone than your body needs, which helps explain the extra acne and body hair. Too much testosterone can also cause cysts in your ovaries which aren't so much cysts as they are immature follicles which started to develop but stopped before they could release an egg.
The most common treatment for PCOS is the birth control pill, which lowers testosterone in a woman's body. Diet and exercise are also recommended. PCOS is associated with diabetes and obesity, and can result in making it difficult to conceive. If you suspect you might have it, consultation with an endocrinologist who specializes in PCOS is highly advisable.