Effect of chronic bromocriptine administration on tumor size in patients with "nonsecreting" pituitary adenomas.

The effect of chronic bromocriptine administration (7.5-20 mg/day for 1-32 months) on the size of "nonsecreting" pituitary adenomas (NPA) was studied in 20 patients. Brain computed tomography showed a marked reduction of the adenoma in one patient after 1 month of treatment (7.5 mg/day); further scans taken 2 and 15 months later, under the same bromocriptine dose, did not show any other variations in the tumoral mass. In the remaining 19 patients, no changes in tumor size were documented by CT during the treatment. Four patients had a worsening of visual fields during bromocriptine administration and they were referred for neurosurgery. In conclusion, bromocriptine was ineffective in reducing tumor size in all but one patient with NPA and, in some cases, it did not prevent tumor growth as is suggested by the worsening of visual fields. Thus, bromocriptine treatment, at least at the doses capable of shrinking macroprolactinomas, seems to be of limited value in patients with NPA.