Bromocriptine treatment over 12 years in acromegaly: effect on growth hormone and prolactin secretion

It is not known whether bromocriptine treatment in acromegaly can be implemented for a life-long period. To elucidate this problem, the secretory GH and PRL states of 12 patients with acromegaly were determined, before bromocriptine treatment, under therapy (15.0 +/- 6.8 mg/day for 12 +/- 3 years; mean +/- SD) and during two-weeks long drug withdrawal after long-term treatment, respectively. Before therapy, all patients showed a non-sufficient GH suppression after oral glucose load (greater than 2 micrograms/l), whereas under dopaminergic treatment the post-glucose GH levels of three patients fell below 2 micrograms/l; normal IGF-I concentrations were found in five patients. However, under bromocriptine, only two patients showed GH suppressions below 2 micrograms/l following glucose, accompanied with normal IGF-I levels. During bromocriptine withdrawal, GH secretion at 60 min in the oral glucose tolerance test increased significantly (17.0 +/- 15.5 vs 5.7 +/- 5.2 micrograms/l; p less than 0.01); the mean IGF-I level rose from 2.1 +/- 0.8 to 4.9 +/- 2.2 kU/l (p less than 0.01). IGF-I was normal during bromocriptine cessation in only one patient; none of the 12 patients showed a GH suppression below 2 micrograms/l after oral glucose load. Under dopaminergic treatment hyperprolactinemia could not be detected. In conclusion, bromocriptine led to a stable suppression of both GH hypersecretion and--if present--concomitantly elevated PRL levels. Severe side effects or a further tumor growth could not be observed. Thus, the data of the longest follow-up investigation that has so far been published indicate that effective life-long bromocriptine therapy seems to be possible in selected patients with acromegaly.