Size reduction of macroprolactinomas by bromocriptine or lisuride treatment.

We have administered to 29 patients with macroprolactinoma the dopamine agonists bromocriptine and lisuride for 1-50 months (mean +/- SE, 12.7 +/- 1.8) in order to assess the effects of these drugs on tumor size. Fourteen patients were treated with bromocriptine (dose range, 7.5-20 mg/day), 12 patients were treated with lisuride (0.6-2 mg/day), and 3 patients were given both drugs. Computed tomography performed before and during treatment showed the occurrence of tumor shrinkage in 18 patients (62%), but in no case was a complete disappearance of the tumor observed. In 5 of these patients, it was even possible to document tumor shrinkage within the first month of treatment with low doses of the dopamine agonists, whereas in other patients, tumors shrank only after prolonged treatment with higher doses. Visual field and acuity improved or normalized in 8 of the 13 patients with visual defects; in some cases, the improvement was reported as early as 2 days after the treatment was started. Plasma PRL levels fell in all patients who showed a reduction in tumor size; in 2 other patients, PRL levels were only poorly suppressed, and tumor size remained unchanged. In the remaining patients, PRL levels were lowered without convincing evidence of tumor shrinkage. In considering the high percentage of patients showing tumor shrinkage under medical treatment, we propose a course with dopamine agonists as the first step in the management of patients with macroprolactinomas regardless of the presence of visual impairments.