Macroprolactin as a Cause of Hyperprolactinemia: Clinical and Radiological Features

Objective: The aim of this study was to determine the prevalence of macroprolactin in patients with hyperprolactinemia in our region, and to determine the clinical and neuroradiological features of the affected individuals. Materials and Methods: We used the Roche Elecsys Prolactin assay (Prolactin II) with polyethylene glycol precipitation to identify macroprolactin; recovery of <= 40% was considered to represent significant macroprolactinemia. Of 156 consecutive patients with hyperprolactinemia, macroprolactin was found in ten (6.4%). Clinical records of these patients were reviewed. Results: Of ten patients with macroprolactinemia, two males presented with infertility and two with decreased libido and erectile dysfunction. Females presented with menstrual dysfunction, with or without infertility. Pituitary adenomas were identified in two of seven patients who underwent neuroimaging. Dopamine agonists were prescribed to seven patients; their symptoms were not affected by this therapy. Conclusions: Macroprolactin is a cause of misdiagnosis and inappropriate treatment in patients with hyperprolactinemia. It is important to be aware of the extent to which the assay system used in the measurement of prolactin may detect macroprolactin, and to have a available validated method to confirm its presence. This will ensure appropriate management for patients with this benign condition.