Abstract: OBJECTIVE To investigate the interaction between serum ferritin (Fer) and parathyroid hormone (PTH), which are the markers of iron metabolism, and their clinical significance in the occurrence and prognosis of peritonitis in patients with end-stage renal disease undergoing peritoneal dialysis (PD). METHODS A retrospective cohort study design was adopted, including 194 patients undergoing PD, who were regularly followed up at Kaifeng Central Hospital from Jan. 1, 2019 to Dec. 31, 2021. Patients were divided into a peritonitis group (135 cases) and a non-peritonitis group (59 cases) based on whether peritonitis occurred. Baseline data and laboratory indicators of patients were collected. The predictive value of Fer and PTH for endpoint events (including all-cause mortality, technical failure, refractory or relapsing peritonitis) was evaluated through Cox proportional hazards regression, Kaplan-Meier survival analysis and nomogram modeling. RESULTS Univariate and multivariate Cox regression analyses indicated that low Fer (<38.40 ng/ml) and low PTH (<157.45 pg/ml) were independent risk factors for the endpoint event (HR were 1.967 and 1.791, respectively, both P<0.001). Survival analysis further revealed that the cumulative incidence of endpoint events was significantly higher in the low Fer and low PTH groups, with the highest risk observed when both were low (P<0.001). The nomogram model constructed based on Fer and PTH demonstrated good calibration and discriminatory ability in predicting the 1-year and 2-year cumulative event incidence rates (with C-index ranging from 0.6 to 0.8). CONCLUSIONS In the acute phase of PD-related peritonitis, the "dual low state" of Fer and PTH can serve as independent biomarkers for predicting poor prognosis, reflecting systemic metabolic disorders and critical conditions under acute inflammatory stress. This study provides a new assessment tool and theoretical basis for risk stratification and individualized intervention in patients with peritonitis.