High Prolactin But Normal MRI Scan

Hi guys

I have had the following prolactin result come back

Serum prolactin level 471 mu/L 86.00 - 324.00mu/L

I have all sides you would expect ED, Fatigue, Weight Gain etc

But my MRI for tumours is normal, any idea what could be causing this and what do I do to treat it? Endo is clueless