A Case of Hyperprolactinemia
Answer: Hyperprolactinemia can be caused by multiple things, the more common ones I see are medication-related and prolactinomas. However, it's important to go back to basics when working these cases up; people can often be wrong (not that they were being malicious in the first place) so it's a good idea to do a confirmatory pregnancy test. In this case, this woman, despite her reassurance to me, turned out to be pregnant.
If the patient was not pregnant and was on no medication that can be implicated, and if the TSH is normal, the next step would be a pituitary MRI.
Bravo to those who answered.