Long-term effects of the combination of pegvisomant with somatostatin analogs (SSA) on glucose homeostasis in non-diabetic patients with active acromegaly partially resistant to SSA

Several recent studies have reported beneficial effects of pegvisomant monotherapy on glucose homeostasis for acromegalic patients resistant to somatostatin analogs (SSA). The aim of our longitudinal study was to test whether these beneficial effects on glucose homeostasis would also occur during combined pegvisomant + SSA treatment amongst partially SSA-resistant acromegalic patients. Ten non-diabetic, partially SSA-resistant acromegalic patients underwent a 12-month SSA+pegvisomant treatment after SSA-only therapy. Glucose homeostasis was evaluated at disease diagnosis, at the end of the SSA treatment and after 6 and 12 months of combined SSA+pegvisomant treatment. The addition of pegvisomant treatment was accompanied by a significant improvement in insulin and glycemic responses to the oral glucose tolerance test, without any significant changes in fasting plasma glucose, glycosylated haemoglobin, homeostatic model assessment-derived insulin resistance index and homeostatic model assessment-derived α-cell function. Moreover, the number of patients with glucose intolerance did not significantly change during the 12-month combined treatment, notwithstanding the significant decrease in serum IGF-1 values. Therefore, our findings suggest that the combined pegvisomant and SSA treatment may not be able to restore normal clinical and biochemical glycometabolic features occurring in acromegalic patients resistant to SSA, while a slight but significant improvement in some biochemical features may be expected.