PTH and systemic inflammatory response syndrome: ALP: alkaline phosphatase; ALT: alanine aminotransferase; APACHE: Acute Physiology and Chronic Health Evaluation Score; AST: aspartate aminotransferase; BISAP: Bedside Index of Severity of Acute Pancreatitis; FiO2: fraction of inspired oxygen; IPN: infected pancreatic necrosis; iPTH: intact parathyroid hormone; PTH: parathormone; PaO2: partial pressure of oxygen; TLC: total leucocyte count; SIRS: systemic inflammatory response syndrome