What hormone can the kidneys EXCRETE? And what is it's function?

Please help....i've been searching everywhere for the answer...and i only find discussion about hormones that are SECRETED and what is excreted because of them. Is my teacher asking this wrong? There are hormones secreted, i already know, by the kidneys...however excretion is the issue in this case, not secretion. Thanks for in advance for the help!