Assessment of macroprolactinemia inpatients with prolactinoma

Abstract

Abstract Purpose Macroprolactin, the high-molecular mass prolactin isoform, is considered to be an inactive product with extrapituitary origin. Although macroprolactinemia is considered a benign condition, there is evidence of overlapping clinical features among patients with hyperprolactinemia. Data on the prevalence of macroprolactinemia in prolactinomas is also quite limited. The aim of this study was to assess the prevalence of macroprolactinemia in our patients with prolactinoma. Methods The study included patients with macroprolactinoma (n=50) and microprolactinoma (n=16). Prolactin level was measured with an electrochemiluminescent immunoassay, and macroprolactinemia was defined as the percentage of prolactin recovery <40% after the polyethylene glycol precipitation. Results Macroprolactinemia was not detected in our patients with prolactinoma (the percentage of PRL recovery range; 55%–96%). The mean percentage of prolactin recovery was similar in patients with macroprolactinoma and microprolactinoma (67.7%±8.0% and 70%±9.4%, respectively, p=0.96). Conclusion Macroprolactinemia is generally associated with negative findings on pituitary imaging. Although the monomeric prolactin is dominant, rarely macroprolactin may also be present in prolactinomas. We did not detect presence of macroprolactin in any of the patients and there was no statistically significant difference between micro- and macroprolactinomas in terms of prolactin recovery.