Birth control pills aren ' t simply pills high in oestrogen which would increase fertility , according to ucaptnmiss ' s logic . They either contain progestin compound very similar to progesterone only the mini pill , helpful for women who are breastfeeding since they don ' t interfere with milk production like the other pills do or they contain both an estradiol and a progestin the combo pill , which is more popular and is the one used to treat PCOS . I ' m not a doctor , but from what I ' ve read PCOS is partially treated with the combo pill because it regulates these hormones , which is the same reason it ' s used to treat other problems related to these hormones from periods that are so painful that you can ' t function in society to periods that never seem to regulate at all . When you take oral birth control , you aren ' t ADDING to the hormones your body is making , you ' re actually REPLACING them . Your body has mechanisms in place to tell it when it has enough of a certain hormone so that it can shut down production so it doesn ' t end up with too much . The pill is just a way to regulate this artificially when your body isn ' t doing as good of a job at it . But it ' s not like taking a vitamin because you ' re deficient in that vitamin , it ' s basically taking control of that whole mechanism because your body isn ' t doing a great job of it naturally .