Interested in feline hormone replacement for spayed teenage cats?

I have my intact dog on an antiestrogenic diet to prevent breast cancer and was toying with the idea of doing the opposite for my elderly but healthy spayed cats. They were spayed/declawed at roughly 6 months. I was three and didn't have any say in the matter. Tigger in particular totally changed when she was spayed. I wish I thought of this years ago. I feed an organic, grain-free, naturally fed (ex grass fed beef and free range soy free chicken) mostly raw home made diet to my puppy, and they get that whenever they want (albeit with extra water) in addition to the Wysong Uretic I have to give them (or Tigger gets a nasty UTI every time) I don't want to give them drugs, but I was thinking of things containing phytostrogen like Mexican Wild Yam, Flax, and possibly even soy or soy lecithin. Does anyone know where I could find out more about this?