I have been diagnosed with hyperprolactinemia. serum level of 97.9.my mri does not show a tumor. what other things can cause this.?

A tumor: You may still have a little one in your pituitary that isn't showing on mri. I suspect that these underlying most cases of "hypothalamic-pituitary dysregulation" as i've found them at autopsy in people who have no idea. Trusting you're healthy otherwise ; not on meds or overstressed; many women with polycystic ovary disease run a somewhat high prolactin. Treatment (if you need it) may be empirical.