Reappraisal of bromocriptine treatment for acromegaly

Abstract

11 acromegalics were treated with bromocriptine for 2--18 months. Their hormonal response was assessed by an acute suppression test with bromocriptine (AST), an oral glucose tolerance test (GTT), and by measuring growth hormone (GH) concentrations during a day of hospital life. The GTTs and the 24-hour profiles were performed before and after bromocriptine. During the AST all patients showed a decrease of GH concentrations ranging from 33 to 86% of the basal. Following bromocriptine, the mean GH concentration was lowered in 7 out of 11 patients during the GTT, and in 8 out of 11 during the profile, but it was within the normal range in 4 patients only during the GTT, and in 1 during the profile. Bromocriptine normalises radioimmunoassayble GH levels in a percentage of patients (12%) which is less than those following conventional treatment of acromegaly, surgery (80%) and pituitary irradiation (70%). Clinically, however, bromocriptine was more effective than judged by the changes of GH levels. Subjective and objective symptoms of acromegaly, such as articular pain, excessive sweating, hypertension, amenorrhoea, urinary hydroxyproline excretion and heel pad thickness decreased in our patients after bromocriptine. A specific action of bromocriptine on the degradation rate of 'little' GH may result in a selective reduction of the bioactive monomeric component of GH and may explain the discrepancy between the clinical and the biochemical response to bromocriptine. This discrepancy might also be explained by a specific action of bromocriptine on the somatomedin levels.