Reversible thioridazine-induced magnetic resonance imaging-documented pituitary enlargement associated with hyperprolactinemia.

Objective: To document a case of reversible thioridazine-induced pituitary enlargement associated with hyperprolactinemia in a patient with schizophrenia.

Methods: We describe a 19-year-old woman with paranoid schizophrenia who was taking thioridazine (a phenothiazine), in whom hyperprolactinemia, galactorrhea, oligomenorrhea, and a reversible anatomic pituitary abnormality developed. Serial magnetic resonance imaging (MRI) studies were used to assess the status of the pituitary gland during various pharmaceutical therapies.

Results: Laboratory evaluation revealed increased serum prolactin (PRL) levels that ranged from 76 to 135 mg/L. Results of thyroid function tests were normal, and gonadotropins and estradiol levels were low, consistent with hyperprolactinemia. MRI revealed asymmetric enlargement of the right side of the pituitary gland. Discontinuing the thioridazine therapy resulted in normalization of the serum PRL and resolution of the pituitary abnormality. Subsequent worsening of the patient's psychiatric condition necessitated a course of electroconvulsive therapy and initiation of treatment with clozapine, a D4 dopamine receptor antagonist. At 1-year follow-up, at which time the patient was maintained on clozapine and was not taking thioridazine, both serum PRL levels and MRI findings remained normal.

Conclusion: Our patient was shown to have asymmetric pituitary enlargement associated with thioridazine-induced hyperprolactinemia, which reversed when use of the drug was discontinued. In patients with serum PRL levels in excess of 100 mg/L during antipsychotic drug therapy, evaluation for a prolactinoma is warranted.