Biochemical diagnosis in prolactinomas: some caveats.

Prolactinomas are the most frequently seen pituitary adenomas in clinical practice. A correct biochemical diagnosis of hyperprolactinemia is a prerequisite for further investigation but may be hampered by analytical difficulties as well as a large number of potentially overlapping conditions associated with increased prolactin levels. Suspicion should rise in patients whose symptoms and biochemical results do not match. Assay problems, macroprolactinemia, and high-dose hook effect are discussed as possible reasons for false positive or false negative prolactin levels. Physiological and pathological causes of hyperprolactinemia and their implications for interpreting prolactin results are reviewed.