Impaired sex hormone production follows. These drugs bind to a receptor on the tumor cell surfaces and initiate a chain of events that lead to decreased cell size, growth and division, and inhibition of prolactin production and release. Fortunately, most macroprolactinomas are responsive to dopamine agonist drugs. As demonstrated by this patient, prolactin levels rarely normalize in those with the giant prolactinomas. We have seen several patients with giant adenomas enjoy dramatic reductions in tumor size and extent as illustrated by this subject of this case study.
Visual abnormalities reverse in nearly all patients who have visual field deficits.
In many cases, the visual deficits resolve within one week of the initiation of medical therapy despite observations that significant reductions in tumor size may require months of continued therapy. Thus, the presence of visual field abnormalities is not necessarily an indication for transsphenoidal pituitary surgery. Lifelong tharapy with dopamine agonist drugs is usually necessary to prevent tumor regrowth.