Pre-Parathyroidectomy PTH as an Integrated Biomarker of Glandular Remodeling and Skeletal Turnover in Secondary Hyperparathyroidism.

Secondary hyperparathyroidism (SHPT) is a major component of chronic kidney disease-mineral and bone disorder (CKD-MBD), reflecting progressive disturbances in mineral metabolism, endocrine signaling, skeletal remodeling, and parathyroid-gland biology. Traditionally, preoperative parathyroid hormone (PTH) has been used primarily as a biochemical threshold for surgical referral. However, persistent PTH elevation in advanced CKD-related SHPT may reflect more than isolated endocrine activity; available evidence suggests it integrates parathyroid-gland remodeling, receptor resistance, skeletal turnover, treatment refractoriness, and systemic CKD-MBD severity. This review summarizes key molecular and cellular mechanisms of progressive SHPT, including diffuse-to-nodular hyperplastic transition, downregulation of calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) signaling, disruption of the fibroblast growth factor 23 (FGF23)-Klotho axis, and activation of transforming growth factor-α (TGF-α)/epidermal growth factor receptor (EGFR) proliferative pathways. Building on this mechanistic framework, we discuss how persistent PTH elevation has been linked to glandular remodeling, resistance to calcimimetic and vitamin D therapy, high-turnover renal osteodystrophy, hungry bone syndrome, altered intraoperative PTH kinetics, postoperative endocrine-skeletal remodeling, and long-term recurrence. Severe SHPT is also increasingly recognized as a systemic CKD-MBD phenotype associated with vascular calcification, cardiovascular risk, metabolic instability, and impaired quality of life. Within this framework, preoperative PTH is best interpreted as an integrated biomarker within a broader assessment of glandular remodeling, skeletal metabolic activity, endocrine resistance, and systemic CKD-MBD biology, rather than as an isolated biochemical threshold.