GSTP1 and autoimmune pancreatitis: In an observational retrospective study performed in 77 AIP-negative acromegalic patients, who were screened for both the AHR rs2066853 variant and the glutathione-S-transferase-P1 (GSTP1) gene promoter methylation, those with the methylated GSTP1 gene promoter were found to be more resistant to SSAs.