Previously surgery and irradiation were the only available procedures to treat patients with
pituitary tumors. During the last few decades, novel drugs such as
dopamine agonists and long-acting
somatostatin analogs were developed and, an alternative medical
therapy emerged. This paper summarizes the effect of medical
therapy on the morphologic features of
pituitary tumors and illustrates the ultrastructural alterations on electron micrographs. Currently drugs can be used in the management of
pituitary tumors secreting GH, PRL, and/or TSH in excess. No medical
therapy is available so far for
ACTH-, FSH-, LH-, or alpha-subunit-secreting
tumors as well as non-
hormone-secreting
pituitary tumors.
Dopamine agonists are effective in the management of PRL-secreting
tumors; they cause marked reversible
tumor shrinkage in the substantial majority of patients. Long-acting
somatostatin analogs are useful in the management of GH- and TSH-secreting
pituitary tumors; they lead to mild to moderate
tumor shrinkage in approximately 50% of cases. In patients treated with these drugs reduction of elevated blood
hormone levels and amelioration of clinical symptoms ensue. It should be emphasized that no permanent cure is obtained. Blood
hormone levels increase and the clinical symptoms reappear after discontinuation of treatment. Recently GH receptor blockers (
pegvisomant) were introduced in the treatment of GH-producing
pituitary adenomas. To the authors' knowledge the effect of these drugs on the morphology of
pituitary tumors has not been revealed so far.