Objective: Asthma is a heterogeneous disease characterized by chronic airway inflammation and variable respiratory symptoms, including episodic dyspnea, cough, wheezing, and chest tightness. While airway inflammation is well established in asthma pathophysiology, data on endothelial dysfunction are limited. Endothelial cell-specific molecule-1 (Endocan), a proteoglycan released by endothelial cells in response to inflammatory stimuli, has recently emerged as a potential biomarker of endothelial injury. This study aimed to investigate serum Endocan levels in asthma patients to evaluate the presence of endothelial dysfunction and explore its relationship with disease severity and control.

Materials and Methods: Fifty asthma patients and 39 healthy controls were enrolled. Participants with systemic comorbidities or active infections were excluded. Asthma severity was classified according to Global Initiative for Asthma (GINA) 2019 criteria, and asthma control was assessed using the Asthma Control Test (ACT). Pulmonary function tests (PFTs) were performed in accordance with the American Thoracic Society (ATS)/European Respiratory Society (ERS) standards. Serum Endocan levels were measured. Statistical analyses were conducted using Student`s t-test, Mann-Whitney U test, Chi-square test, and Spearman correlation analysis. A p-value <0.05 was considered statistically significant.

Results: The asthma and control groups did not differ in age, sex, BMI, or smoking status. While forced expiratory volume in one second (FEV₁) and FEV₁/forced vital capacity (FVC) ratios were significantly lower in asthma patients, serum Endocan levels were notably higher (p<0.001). However, Endocan levels did not differ significantly across asthma severity groups or between controlled and uncontrolled asthma. No significant correlations were observed between Endocan levels, ACT scores, or pulmonary function parameters.

Conclusion: Higher Endocan levels in asthma patients suggest that endothelial dysfunction may contribute to asthma pathophysiology. However, the lack of association with disease severity and control limits its potential as a monitoring biomarker. Further prospective studies are warranted.