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

Abstract

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 (>2 μg/l), whereas under dopaminergic treatment the post-glucose GH levels of three patients fell below 2 μg/l; normal IGF-I concentrations were found in five patients. However, under bromocriptine, only two patients showed GH suppressions below 2 μg/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 μg/l; p<0.01); the mean IGF-I level rose from 2.1±0.8 to 4.9±2.2 kU/l (p <0.01). IGF-I was normal during bromocriptine cessation in only one patient; none of the 12 patients showed a GH suppression below 2 μg/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.