Nephrotic-Range Proteinuria in a Patient With a Giant Prolactinoma

We report for the first time a case of nephrotic-range proteinuria adequately controlled by using dopamine agonists. A 40-year-old man was studied because of persistent asymptomatic nephrotic proteinuria despite lifestyle modifications and treatment with converting enzyme inhibitors. The renal biopsy specimen did not show histopathologic changes. In the follow-up period, a giant prolactinoma was found by chance with extremely high prolactin (PRL) values. After establishing cabergoline therapy, we achieved a remarkable decrease in both serum PRL levels and tumor mass, and surprisingly, proteinuria disappeared. We discuss the possible pathogenic mechanisms of proteinuria that may correspond to PRL level in urine (prolactinuria) or another tumor-related protein.