Evaluating the role of vitamin D metabolites and intact parathyroid hormone across chronic kidney disease stages

Background: Chronic kidney disease (CKD) is defined as abnormal kidney structure or function that last over three months.  Its prevalence increases with age, affecting 38% of individuals aged 65 years and older. Key biomarkers for assessing CKD severity include a low estimated glomerular filtration rate (eGFR) and increased albumin levels in urine, determined by the albumin-to-creatinine ratio (ACR). 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D are impaired in CKD patients due to reduced renal function, leading to deficiencies in active vitamin D forms and contributing to secondary hyperparathyroidism (SHPT). This study evaluated the role of vitamin D metabolites and intact parathyroid hormone levels in different stages of CKD.
Subjects and Methods: This cross-sectional study was performed at the Al-Imam Al-Sadiq Hospital in Babil, Iraq. This study included 164 patients (84 males and 80 females) with CKD stages 2-5. Patients were divided into groups based on CKD stage: 20 patients with stage 2 and 36 patients with stages 3a, 3b, 4, and 5. Blood samples were collected for the serum analysis of urea, creatinine, 25 (OH) D, 1,25 (OH)2 D, and intact PTH levels. Urine samples were collected to assess microalbuminuria. ELISA was used for vitamin D and PTH measurements, while standard biochemical methods were employed for the other parameters.
Results: 1,25 (OH)2 D and 25 (OH) D levels   significantly declined with advancing CKD stage (p ≤ 0.001), while iPTH levels increased significantly (p ≤ 0.001). The 1,25VitD/iPTH ratio decreased significantly across the CKD stages (p ≤ 0.001).
Conclusion: The study concluded an important association between deteriorating CKD (renal destruction), declining vitamin D metabolites (25 OH D, 1,25 OH D), and elevated iPTH levels.