Features of mineral and bone metabolism in patients with secondary hyperparathyroidism and chronic kidney disease: a cohort study

BACKGROUND: Patients with chronic kidney disease stage 5 and secondary hyperparathyroidism remain at high risk for osteoporosis and metabolic disturbances; however, the precise relationships between parathyroid hormone (PTH) levels, mineralbone and lipid parameters remain insufficiently understood.

AIM: To assess features of mineral and bone metabolism and the severity of extraskeletal calcification in patients with chronic kidney disease stage 5D and secondary hyperparathyroidism, and their associations with age, PTH levels, lipid profile, and mortality risk.

METHODS: The study included 111 cases from a local registry of the Nephrology Department at Tomsk Regional Clinical Hospital (2017–2023), which contained data on 1,884 patients. Inclusion criteria were: age 18–90 years; confirmed CKD stage 5D; renal replacement therapy duration ≥6 months; presence of secondary hyperparathyroidism. Exclusion criteria were: malignancies; primary hyperparathyroidism. Clinical, demographic, laboratory, and instrumental parameters were analyzed in all patients; extraskeletal calcification was assessed (carotid ultrasound and cardiac valve echocardiography), bone mineral density (densitometry), and mineral and lipid metabolism markers were measured. For statistical analysis, the Mann–Whitney, Kruskal–Wallis, Pearson chisquare, and Fisher exact tests, and Spearman rank correlation analysis were used. Risk factors were assessed using binary logistic regression; prognostic value was evaluated using ROC analysis. Differences were considered statistically significant at p < 0.05.

RESULTS: High PTH levels were observed (median 421 pg/mL); target values were achieved in only 27.9% of patients. Despite ongoing therapy, marked mineral disturbances persisted: hyperphosphatemia in 57.7% of patients, vitamin D deficiency (median 13.8 ng/mL), and dyslipidemia. Extraskeletal calcification was found in 79.2% of patients (systemic in 45%), and osteoporosis in 72%. Correlation analysis showed significant associations between age and osteoporosis (ρ = 0.540; p < 0.01), vascular calcification severity (ρ = 0.277; p = 0.003), and alkaline phosphatase levels (ρ = 0.193; p = 0.045). Higher PTH levels positively correlated with mortality (ρ = 0.242; p = 0.02). Dialysis duration was associated with vitamin D levels (inverse correlation), creatinine, and alkaline phosphatase activity. ROC analysis confirmed the prognostic value of PTH for mortality (AUC = 0.648; p = 0.021) and its association with the severity of extraskeletal calcification.

CONCLUSION: A high frequency of extraskeletal calcification, osteoporosis, and severe mineral disturbances was found in patients with chronic kidney disease and secondary hyperparathyroidism. Elevated PTH levels were associated with the risk of systemic calcification and mortality, while age was a key factor in the development of osteoporosis.