Is pasireotide-induced diabetes mellitus predictable? A pilot study on the effect of a single dose of pasireotide on glucose homeostasis

Introduction: Pasireotide (PAS) is an effective treatment for Cushing’s disease (CD) but its use is burdened by an associated high incidence of diabetes mellitus (DM). The aim of this study was to examine the effect of a single subcutaneous injection of PAS on glucose metabolism in CD, and to identify predictors of DM onset. Methods: Fifteen patients with CD (13 females, 2 males; median age 43 years [IQR 34–50]) were submitted to an acute PAS test (600 µg s.c.), measuring glucose, insulin, C-peptide, GIP, glucagon, GLP-1, ACTH, and cortisol at the baseline and every 30 min for 2 h. Then they were treated twice daily with PAS 600 µg, and followed up with clinical and hormone assessments for a median of 6 months [2–13]. Results: PAS prompted a significant decrease in all hormonal parameters considered except for glycemia, which increased (as expected), reaching the highest value at 120′ (p < 0.0001). Overall, 9/15 patients developed DM within 2 months of starting PAS therapy. There were no differences in age, weight, visceral adiposity, HOMA index, fasting glucose or severity of CD between patients who developed DM and those who did not. Baseline fasting glucagon levels were higher in the DM patients (17.95 [12.45–20.54] vs. 10.53 [8.11–12.33] pmol/L, p = 0.0256), and so were GIP and HbA1c levels (37 [5.5–39.5] vs. 29 [27–31.8] mmol/mol, p = 0.0008). Glucose at 120′ was also significantly higher in the DM patients (9.5 [8.65–11.95] vs. 6.85 [4.48–9] mmol/L, p = 0.012). Conclusions: PAS was rapidly able to suppress insulin and incretin secretion, with a subsequent rise in glucose levels into the diabetic range. It also induced a significant inhibition of glucagon production. The patients at higher risk of DM during PAS therapy were those with higher glucagon levels, HbA1c > 34.5 mmol/mol, and a glucose peak after PAS administration > 9 mmol/L. CD patients with these features given PAS therapy should therefore be monitored more carefully.