Saw palmetto contains a weak form of an Alpha5-reductase enzyme inhibitor. So it will reduce conversion of testosterone to DHT (dihydrotestosterone). DHT is what builds muscle mass and causes male pattern baldness (aka androgen alopecia). It will not interfere with estrogen and androgen blocker medications but getting a prescription for Finesteride or Duteraside will be more effective. These medications are dosed amounts of alpha5-reductase inhibitors.
Now a warning. There is a seemingly permanent medical condition that some people have had caused by these medications and also saw palmetto. I've read about it and is sometimes called Finestride Syndrome. It is a permanent reduction in the bodies ability to produce alpha5-reductase enzyme. For men taking it for prostate issues or hair loss its a big deal. Also blocking the A5-reductase enzyme can have mental side effects so definately talk to your doctor about potential side effects.
I was using saw palmetto in the three months I was waiting for my letter from my therapist to begin HRT. For me it was fine. I had low enough T levels that just that and other diet related things to reduce T production caused me to drop into PMS land.

I would strongly suggest not getting there! Your brain needs one of the sex hormones to function correctly. Without either, well lets just say it is bad mentally.