Background/Objectives: This study aimed to evaluate the discriminative performance of routine systemic inflammation- and nutrition-based indices for distinguishing histopathologically confirmed gastric malignancy from non-malignant endoscopic findings. Methods: This retrospective case–control study included 211 patients who underwent upper gastrointestinal endoscopy with histopathological evaluation: 139 non-malignant endoscopic controls (129 benign/non-neoplastic and 10 premalignant findings) and 72 gastric malignancy cases. Premalignant lesions were not considered malignant outcomes. Discrimination was evaluated using univariable ROC analyses and multivariable logistic models. The fixed predictor set was assessed using 10-fold out-of-fold validation and 500-resample bootstrap optimism correction; a separate fully nested selection-inclusive audit was used to quantify uncertainty arising from variable selection. Results: NLR (AUC = 0.792), INR (AUC = 0.791), and SIRI (AUC = 0.783) showed the highest univariable discrimination. Among the variables retained in Model 1, higher ESR and RDW, lower MPV and HDL, higher INR values, and male sex showed statistically significant multivariable associations. Model 1 had an apparent AUC of 0.928 (95% CI, 0.890–0.959), a fixed-set 10-fold out-of-fold AUC of 0.890, and a bootstrap optimism-corrected AUC of 0.901. A fully nested selection-inclusive audit yielded an out-of-fold AUC of 0.873 and a bootstrap-corrected AUC of 0.869. Conclusions: Routine inflammation- and nutrition-related laboratory measures discriminated gastric malignancy from non-malignant endoscopic findings in this endoscopy-selected cohort. The model remains exploratory and requires prospective external validation. These data do not establish screening performance or diagnostic accuracy for early or asymptomatic gastric cancer.

Background/Objectives: Hashimoto’s thyroiditis (HT) is associated with autoimmune thyroid inflammation, but its systemic inflammatory, immunonutritional, and atherogenic lipid profile across thyroid functional groups remains insufficiently characterized. This study aimed to evaluate routinely available inflammatory, immunonutritional, and atherogenic indices across the HT spectrum and to examine their relationships with thyroid function and autoimmunity. Methods: This retrospective study included newly diagnosed, untreated adult patients with HT and healthy controls without documented comorbidities. After exclusions and propensity score matching for age, sex, and body mass index, 148 patients with HT and 74 controls were analyzed. Patients with HT were classified as euthyroid HT (EH, n = 62), subclinical hypothyroidism (SCH, n = 47), or overt hypothyroidism (OH, n = 39). A total of 44 demographic, thyroid-related, hematologic, biochemical, lipid, inflammatory, immunonutritional, and atherogenic variables were evaluated. Elastic Net–penalized logistic regression, multivariable logistic regression, correlation analysis, and receiver operating characteristic curve analysis were performed. Results: HT was associated with a distinct systemic profile characterized by higher inflammatory and atherogenic indices and alterations in immunonutritional indices. Across the control, EH, SCH, and OH groups, systemic inflammation response index (SIRI; 0.5 vs. 0.8 vs. 1.0 vs. 1.4, p < 0.001) and atherogenic index of plasma (AIP; 0.1 vs. 0.3 vs. 0.5 vs. 0.8, p < 0.001) showed an ascending pattern, whereas prognostic nutritional index (PNI; 56.0 ± 3.2 vs. 50.2 ± 6.0 vs. 46.8 ± 5.5 vs. 40.6 ± 7.0, p < 0.001) showed a descending pattern. In multivariable models, SIRI and AIP were independently associated with EH compared with controls, whereas SIRI, AIP, and PNI were independently associated with SCH compared with EH and with OH compared with SCH. SIRI and AIP showed strong positive correlations with thyroid-stimulating hormone and negative correlations with free thyroxine, while PNI showed the opposite pattern. These indices also differed significantly according to anti-thyroid peroxidase and anti-thyroglobulin antibody status. Conclusions: Distinct inflammatory, immunonutritional, and atherogenic lipid profiles were observed across HT groups. SIRI and AIP may reflect systemic alterations even in EH, whereas lower PNI may reflect immunonutritional alterations associated with SCH or OH.