Is it possible to have an adenoma/prolactinoma and have normal periods?

Yes: If the prolactin level is only a little elevated, a woman can have regular periods. A woman might or might not be ovulating with each cycle, and so might or might not not be able to become pregnant. However, a woman with a prolactinoma should use a reliable birth control method if she does not wish to become pregnant.

Menses: It is possible but very unusual and normally related to how high the level of prolactin is in the blood, the higher the level the more likely the cycle will be interrupted.