A lot of people take spiro for a few weeks before starting estrogen to test for allergic reactions, but if you're on it long term with no estrogen it can hurt your bones or cause depression. As for effects (listing only the ones E would give you as well)--you may experience decreased libido, onset of gynecomastia, a decrease in energy, and no further puberty (but that's unlikely at your age). However, I'm not sure of the prevalance of any of these results, so you should probably discuss it with a doctor if you're debating because they can tell you if it's likely there'll be negative effects and what it will do exactly.