Insulin secretion improvement during steroid therapy for autoimmune pancreatitis according to the onset of diabetes mellitus.

BACKGROUND

Autoimmune pancreatitis (AIP) is frequently complicated by diabetes mellitus (DM), but DM associated with AIP is reported to improve after steroid therapy. The aim of this study is to investigate glucose intolerance during steroid therapy according to the onset of DM.

METHODS

Sixty-one patients who underwent steroid therapy for AIP were included into this study. We evaluated C peptide index (CPI), homeostasis model assessment for insulin resistance (HOMA-R), and the pancreatic diameter at AIP diagnosis and after 4 weeks, 1 year, and 2 years of steroid therapy. Patients were categorized into three groups according to DM onset: Pre-existing DM (pDM), concurrent DM (cDM), and non-DM (nDM).

RESULTS

Forty-three patients (71%) had DM: 15 pDM and 28 cDM. At AIP diagnosis, CPI was lower in patients with pDM (0.7, P = 0.007) and cDM (0.9, P = 0.018) than nDM (1.3). After 4 weeks of steroid therapy, CPI improved in cDM (P < 0.001) and in nDM (P = 0.021). After 2 years of steroid therapy, HOMA-R increased (2.1-3.0, P = 0.007) but CPI gradually improved (1.0-2.1, P = 0.004). DM improved in 23% of cDM, and 55% of insulin users in cDM discontinued using insulin. Pancreatic atrophy was seen in 30%, and was associated with DM.

CONCLUSION

DM in patients with AIP was associated with impaired insulin secretion rather than insulin resistance. Insulin secretion improved during steroid therapy for AIP in patients with concurrent DM. Thus, glucose intolerance can be an indication for AIP treatment.