What do pill hormones do?

The pituitary gland - the tiny gland in your brain that controls the levels of hormones in your body - doesn't work on its own. It needs feedback in order to perform its functions. When you're on the pill, this gland receives information that the progesterone level is high, indicating that a fertilised egg is already in the system. Of course, this is not the case and the high progesterone level is mimicked by the progestogen from the pill. But the pituitary gland then stops the ovaries from producing any more ripe eggs. This is the main way the pill works, by preventing ovulation. It also thickens the mucus at the entrance to the womb, making it thick and sticky and difficult for sperm to get through.