Cabergoline in the treatment of acromegaly : a study in 64 patients.

Cabergoline is a new, long acting, dopamine agonist that is more effective and better tolerated than bromocriptine in patients with hyperprolactinemia. Because dopamine agonists still have a place in the medical management of acromegaly, cabergoline might be a useful treatment. We, therefore, evaluated the effect of long term administration of cabergoline in a large group of unselected acromegalic patients. Sixty-four patients were included in a multicenter, prospective, open labeled study. A subgroup of 16 patients had GH-/PRL-cosecreting pituitary adenomas. Cabergoline was started at a dose of 1.0 mg/week and was gradually increased until normalization of plasma insulin-like growth factor I (IGF-I) levels, occurrence of unacceptable side-effects, or a maximal weekly dose of 3.5 mg (7.0 mg in 1 case) was reached. Treatment with cabergoline suppressed plasma IGF-I below 300 micrograms/L in 39% of cases and between 300-450 micrograms/L in another 28%. With pretreatment plasma IGF-I concentrations less than 750 micrograms/L, a suppression of IGF-I below 300 micrograms/L was obtained in 53% of cases, and a suppression between 300-450 micrograms/L was obtained in another 32%. By contrast, with pretreatment plasma IGF-I concentrations above 750 micrograms/L, only 17% of cases showed a suppression of IGF-I below 300 micrograms/L, and there was IGF-I suppression between 300-450 micrograms/L in another 21%. In GH-/PRL-cosecreting adenomas, 50% of cases suppressed plasma IGF-I levels below 300 micrograms/L, and another 31% did so between 300-450 micrograms/L, in contrast to only 35% and 27%, respectively in GH-secreting adenomas. Similar results were obtained concerning the secretion of GH. Tumor shrinkage was demonstrated in 13 of 21 patients, with a mass reduction by more than half in 5 GH-/PRL-cosecreting adenomas. Except for slight gastrointestinal discomfort and orthostatic hypotension in a few patients at the beginning of therapy, cabergoline treatment was well tolerated. Only 2 patients stopped medication because ...