Giant cabergoline-resistant prolactinoma in a man who presented with a psychotic episode during treatment: a case report

Prolactinomas are tumors of the pituitary gland that usually respond very well to treatment with cabergoline. Resistance to cabergoline is very rare, but when it occurs, it is a difficult problem to resolve if the tumor is inoperable. A 62-year-old white man was treated for a giant macroprolactinoma detected during investigation of a subacute subdural hematoma of the left frontal lobe. The patient was treated with cabergoline for 17 years with a dose ranging from 1.0 mg to 3.5 mg per week. We were not able to normalize his prolactin level, which initially was 14,992 ng/ml and ultimately 1754 ng/ml. The tumor significantly shrank during the follow-up period but persisted. The patient had cardiac valvulopathies that did not worsen. He had an ischemic stroke and developed a psychotic condition that was successfully treated by lowering the cabergoline and administering quetiapine and mirtazapine together. This regimen led to a small increase in the patient's prolactin that returned to previous levels and remained as such until the last medical evaluation. The tumor continued to shrink and had a cystic degeneration in the last evaluation. Combined use of cabergoline with quetiapine and mirtazapine to treat a psychotic crisis may have contributed to shrinking the tumor in our patient because these antipsychotics have action mediated by growth factors that interfere with growth of pituitary tumors.