The consequences of an untreated prolactin secreting pituitary adinoma can be severe, damage to optic nerves. MRI's are costly, so one does not do this without reason. Secondary hypogonadism can also be from other adinomas and also from physical damage from blows to the head that can sometimes be seen with an MRI.
Prolactin secreting adinomas seem to show up with younger guys.
A prolactin secreting adinoma is typically so well managed with Dostinex/cabergoline, one also does not want to miss that opportunity.
With normal prolactin, MRI's are not justified and even with high prolactin, many docs want it to be higher. I am convinced that some elevated prolactin levels may be harmful and advocate a trial of Dostinex to see where prolactin and LH/FSH go. This is quite inexpensive and diagnostic. If one did feel better ...