A new and useful tool for differentiating prolactinomas from non-functioning pituitary adenomas: a pilot study of the cabergoline disconnection test.

Objective: Clinical, imaging, and laboratory differentiation between non-functioning pituitary adenomas (NFPAs) and prolactinomas can be challenging in clinical practice because of their similar presentation and eventual overlap in prolactin levels. The degree of prolactin suppression after a single low-dose cabergoline administration may be useful as a test to discriminate between these two clinical conditions and to determine the choice of therapy (dopamine agonist versus neurosurgery).

Methods: This retrospective cohort study included 19 patients with macroadenomas (11 NFPAs and 8 prolactinomas) whose prolactin levels were evaluated at baseline and 48 h after receiving a single dose of 0.25mg cabergoline. A receiver operating characteristic curve was generated for sensitivity and specificity analyses.

Results: The baseline median prolactin level was 58ng/mL (range, 32.5-151.2ng/mL) in the NFPA Group, which was significantly lower than that observed in the Prolactinoma Group (733.7 [range, 180-6941ng/mL]) (p<0.001). After the cabergoline disconnection test, the NFPA Group exhibited a lower absolute prolactin level (p<0.001) and a higher percentage of prolactin reduction (p=0.004). The post-test prolactin level ≥26.3ng/mL had 100% sensitivity and specificity in identifying prolactinomas. When using the percentage of reduction, post-test prolactin reduction ≥85.6% had 54.5% sensitivity and 100% specificity to differentiate NFPAs from prolactinomas.

Conclusion: A single low-dose oral cabergoline is a fast and inexpensive test for use in daily clinical practice to discriminate between hyperprolactinemia due to NFPAs and prolactinomas, with high sensitivity and specificity.