Bromocriptine treatment of acromegaly: possible dose dependency of the tumor size-reducing effect.

The effect of long-term, high-dose therapy with bromocriptine (BR) on the clinical and hormonal response, tumor size and neuro-ophthalmological status was studied in seven acromegalic patients. The mean BR dose was 64 mg/day (range 35 to 80) for a mean period of 11 months (range 10 to 12). In six patients there was a clinical improvement already manifest at low BR doses (10 to 20 mg). Serum growth hormone levels fell substantially (greater than 50%) in five patients, and the growth hormone response to thyrotropin-releasing hormone (TRH) and glucose were similar to those previously reported at lower doses of the drug, as were the prolactin and thyroid-stimulating hormone responses to TRH. In three patients, repeat CT scan disclosed a reduction in tumor size. In none of the patients was there evidence of tumor progression, with the possible exception of one patient who developed an impairment of the visual evoked potential response. These results suggest that when compared to previous studies in which lower doses of BR were used, a high BR dose is not superior in terms of clinical response and hormone secretion, but does appear to increase the percentage of patients who respond with a reduction in tumor size.