Diabetes mellitus in pheochromocytoma and paraganglioma: Prevalence, dynamics of insulin secretion / sensitivity and predictors of remission

Background and aims Pheochromocytoma and paraganglioma (PPGL) are associated with dysglycemia and diabetes mellitus (DM) much of which improves post operatively. In this study, we set out to ascertain pre and post-operative prevalence of DM in patients with PPGL based on oral glucose tolerance test (OGTT) and HbA1c and to evaluate effect of insulin secretion and sensitivity indices on DM pre-operatively. Methods Clinical and anthropometric data collection, HbA1c, 75 g OGTT with serum insulin estimation were done pre-operatively (n = 34) and at follow-up after successful surgery (n = 24) in patients with PPGL. Results Pre and post-operative prevalence of DM were 48%(18/37) and 17% (4/24) respectively. Comparison of patients with highest (Q4) and lowest (Q1) quartiles of insulinogenic index (IGI),a parameter of insulin secretion, revealed trends towards higher prevalence of DM in patients with lower IGI (Q4 to Q1: 29% versus 71%,n = 28, p = 0.24)but no association was observed with HOMA-IR (Q4 to Q1:50% versus 57%, n = 28, p = 1.00), an insulin sensitivity index. DM remitted in 77% patients post-operatively, predicted by duration of DM of Conclusion There is high prevalence of DM in PPGL, with marked remission post-operatively, especially predicted by shorter duration of DM. Impaired insulin secretion is more strongly associated with pre-operative DM than increased insulin resistance.