Does saw palmetto decrease libido and sex drive?

Saw palmetto has no value in genetic male pattern balding. There is really no data on side effects. There is probably no harm in trying it.

This product has not been scientifically proven to decrease hair loss and may decrease libido and sexual drive. There are two products that are FDA approved and proven to decrease or slow down genetic hair loss and they are propecia and rogaine. 

You are using saw palmetto
which will have no value and you are wasting your time as your hair loss
progresses. In theoury, it might reduce your sex drive but my experience with this drug is limited to what I read about it. Many men under 30, will stop or reverse the thinning that occurs
with genetic balding with the drug finasteride. I also always perform bulk
measurements with an instrument called HAIR CHECK which is a good way to
determine just how much thinning you have that you can not see. Once this test
is done and you have gone a year, I often repeat the test as it gives an
excellent measurement on what happened to your hair over the year. If it got
better and some of the thinning reversed, maybe you won't need a transplant and
that is the goal that you should look to do. Of course, a good doctor is
critical to this course.