The importance of routine screening for macroprolactin in symptomatic patients with idiopathic hyperprolactinemia

Objective: To evaluate the importance of screening for macroprolactin in symptomatic patients with apparent idiopathic hyperprolactinemia. Methods: During 20 months, the prevalence of macroprolactinemia was evaluated among consecutive symptomatic female patients with apparent idiopathic hyperprolactinemia routinely followed in two neuroendocrinology reference centers from Recife. This prevalence has never been systematically evaluated. Results: A total of 82 patients (mean age, 36.1±7.3 yrs; age range, from 25 to 50) were included; 69 of them (84.1%) had been treated with cabergoline. The screening for macroprolactin was positive in 22 patients (26.8%), 15 of whom (68.2%) misleadingly received longterm treatment with cabergoline. The clinicaland demographic features, as well as baseline prolactin levels, were comparable in patients with true idiopathic hyperprolactinemia and in those with macroprolactinemia. Conclusion: Macroprolactinemia was found in about one quarter of the patients with apparent idiopathic hyperprolactinemia. Our findings highlight the importance of routine screening for macroprolactin in all patients with idiopathic hyperprolactinemia, regardless their clinical features, in order to avoid misdiagnosis and unnecessary treatment with dopamine agonists.