What Causes Elevated FSH Level In Blood With History Of Testicular Cancer?

My wife and I are trying to have children, so I had some blood work done. It has came back that my fsh is high. My spermed checked out to be great, but my testosterone is low. I had testicular cancer 12 years ago and went through kemo and lost one testical. I am just seeing if I should be worried about the fsh level being high and can this be a cancer marker?