Effect of bromocriptine withdrawal in acromegaly on body composition as assessed by bioelectrical impedance analysis

Abstract

Abstract. To evaluate the effect of bromocriptine withdrawal after dopaminergic long-term treatment (15.0±6.8 mg/day, mean ±sd) in 12 acromegalic patients on body composition, bioelectrical impedance was measured before and at the end of two weeks of drug withdrawal. During withdrawal basal hGH and IGF-I increased from 2.5±1.9 μg/l and 2.1±0.8 kU/l to 9.1±11.7 μg/l and 4.9±2.2 kU/l, respectively, and the hGH secretion deteriorated significantly both after oral glucose load and in the TRH test, indicating recurrence of active acromegaly. Reactance and resistance decreased by 5±4 and 23± 19 Ω respectively (p<0.01), whereas body weight remained constant (+0.4±2.1 kg). Bioelectrical impedance analysis indicated evident shifts in body composition, i.e. a significant reduction of body fat (−2.0±1.7 kg) and a simultaneous increase in both lean body mass (+2.4±2.2 kg) and total body water (+1.8± 1.6 l). The changes in body composition were related to a combined effect of unsuppressed hypersomatotropism and the lack of bromocriptine actions other than inhibition of hGH secretion (for example stimulation of the renin-angiotensin-aldosterone system by both the recurred hypersomatotropism and the absence of dopaminergic bromocriptine effects). We conclude that bioelectrical impedance analysis is a good additional tool to assess the pathophysiological effects of bromocriptine withdrawal in long-term treated acromegalic patients.