Discrimination of prolactinoma from hyperprolactinemic non-functioning adenoma

The objective of this study was to evaluate characteristics that discriminate prolactinoma from non-functioning pituitary macroadenoma with hyperprolactinemia. We included 117 patients with hyperprolactinemic pituitary macroadenomas. Patients were divided into three groups according to treatment outcomes and pathologic results: (A) prolactinoma that responded to dopamine agonist (DA) treatment (PRDA); (B) prolactinoma requiring surgical treatment (PRS); and (C) non-functioning pituitary adenoma with hyperprolactinemia (NFPAH). Old age, low serum prolactin levels, and extrasellar extension were associated with NFPAH. Most patients with NFPAH had serum prolactin levels less than 100 ng/ml. Visual defects and GH deficiency were more common in patients with NFPAH compared with patients with PRS and PRDA, without difference of tumor size. Galactorrhea and amenorrhea were less frequent in patients with NFPAH than in patients with PRS and PRDA. Post-operative remission of hyperprolactinemia was achieved in 100% of patients with NFPAH and in 72.5% of patients with PRS. DA administration was required in 25.5% of patients with PRS; however, no patients with NFPAH required DA administration. In conclusion, old age, extrasellar tumor extension with relatively low prolactin levels, visual defect, and GH deficiency were considered suggestive of non-functioning pituitary adenoma rather than prolactinoma in hyperprolactinemic pituitary macroadenoma.