The acute effect of a single application of cabergoline on endogenous GH levels in patients with acromegaly on pegvisomant treatment

Abstract

Objective Treatment with pegvisomant, an antagonist of growth hormone (GH) receptors, increases GH levels in a dose dependent manner. Cabergoline can suppress GH secretion in approximately 40% of acromegalic patients. However, the acute effects of cabergoline have not been studied in patients treated with pegvisomant. We performed this cross-sectional study to evaluate endogenous GH after an additional single cabergoline administration. Design 9 acromegalic patients on pegvisomant therapy were included. A 6 h GH profile after pegvisomant alone (P) and a 9 h profile in combination with oral cabergoline 0.5 mg (PC) were performed. After 3 or 6 h, all patients received a standardized light mixed meal. Endogenous serum GH and pegvisomant levels were measured by special in-house assays. The GH assay showed no interference with pegvisomant. Results Endogenous GH levels at baseline did not differ significantly between the profiles (P: 16.5 μg/l (range 3.2–36.6 μg/l), PC: 8.0 μg/l (1.6–48 μg/l), p > 0.05). In both profiles, GH fluctuated before meal. GH decreased more pronounced in PC but this decrease was not statistically significant. After meal, a significant decline in endogenous GH levels from 16.4 μg/l (0.4–27.1 μg/l, 100%) to 8.1 μg/l (0.2–24.7 μg/l, 66%) appeared in P at 300 min (p < 0.01). Also in PC a decline from 7.8 μg/l (1.1–29.6 μg/l, 100%) to 5.2 μg/l (0.4–23.9 μg/l, 75%) at 300 min was observed but it was not significant. Conclusion Endogenous GH is not significantly decreased after a single oral cabergoline application during pegvisomant treatment in acromegaly.