Correlation of Parathyroid Hormone Values With Lung Function Parameters in Patients With Chronic Obstructive Pulmonary Disease

Objectives: The aim of this study was to determine the disturbances in the concentration of parathyroid hormone (PTH) and 25-hydroxyvitamin D (vitamin D) in patients with stable chronic obstructive pulmonary disease (COPD) and its correlation with airflow obstruction. Materials and methods: A prospective study included 200 patients with a confirmed diagnosis of COPD in the Department of Lung Diseases and Tuberculosis and Pulmonology Polyclinic of University Clinical Hospital Mostar in the period of three years, between May 2021 and May 2024. Inclusion criteria were a stable phase of COPD, hemodynamically stable patients older than 40 years, forced vital capacities in the first second (FEV1)/forced vital capacities (FVC) <0.7, and patients with PTH, vitamin D, calcium, and phosphate measurements. Exclusion criteria were acute exacerbation of COPD in the last month; current treatment with nutritional supplements, vitamins, and statins; lack of availability of lung function data; use of systemic corticosteroids in the previous three months; chronic renal insufficiency, respiratory diseases other than COPD (asthma, pneumonia, tuberculosis, and bronchiectasis), and other diseases (cancer and parathyroid disease). Medical records about demographic data (age and gender), pulmonary function test (FVC, FEV1, FEV1%FVC, mean expiratory flow (MEF)50), body mass index (BMI), COPD assessment test (CAT), Modified Medical Research Council (mMRC) Dyspnea Scale, and serum PTH, vitamin D, calcium, and phosphate levels were obtained. Results: Patients with higher COPD stage had lower spirometry values, most significantly MEF50. The higher the COPD group (Global Initiative for Chronic Obstructive Lung Disease (GOLD) D), the lower vitamin D and the higher PTH levels were. Calcium and phosphate values were the same for all groups. Vitamin D and PTH levels significantly correlated with MEF50 values. The lower MEF50 level, the higher PTH levels, and lower vitamin D levels were found (P<0.05). Conclusion: Our study showed that the patients in the higher COPD group have lower vitamin D levels and higher PTH levels, indicating that they developed secondary hyperparathyroidism. The levels of vitamin D and PTH correlated the most with MEF50 values while other spirometry parameters did not significantly correlate with vitamin D and PTH levels.