Endocrine Abstracts

JOINT3456

Background: Primary hyperparathyroidism (PHPT) is a common endocrine disorder classified into hypercalcemic and normocalcemic subtypes. Traditional biochemical markers such as serum calcium, phosphorus, and parathyroid hormone (PTH) aid in diagnosis; however, additional markers may improve diagnostic accuracy. The chloride-to-phosphorus (Cl/P) and chloride-to-magnesium (Cl/Mg) ratios have been proposed as novel biomarkers for distinguishing PHPT subtypes and predicting skeletal and renal complications.

Methods: A retrospective observational study was conducted on 116 PHPT patients who underwent parathyroidectomy at Ankara Bilkent City Hospital from 2019 to 2022. Preoperative clinical and biochemical parameters, including serum Cl, P, and Mg levels, were analyzed. Cl/P and Cl/Mg ratios were calculated and correlated with PHPT subtypes and complications such as bone mineral density (BMD) loss and nephrolithiasis.

Results: The Cl/P ratio was significantly higher in patients with hypercalcemic PHPT compared to those with normocalcemic PHPT (median 42. 4 vs. 38. 3, P = 0. 0125). ROC curve analysis determined that a Cl/P ratio greater than 43. 6 had a specificity of 80. 0% and a sensitivity of 43. 4% (AUC: 64. 1%) in distinguishing PHPT subtypes. Additionally, the Cl/P ratio was lower in patients with osteopenia and osteoporosis (p < 0. 0001), suggesting its role in predicting skeletal complications. The Cl/Mg ratio, on the other hand, was significantly associated with nephrolithiasis risk. A cut-off value of ≤55 demonstrated 82. 4% sensitivity and 66. 7% specificity (AUC: 70. 5%, P = 0. 0002) in identifying patients at risk for nephrolithiasis. However, the Cl/Mg ratio did not show a significant difference between PHPT subtypes.

Discussion: The Cl/P ratio demonstrated potential as a diagnostic adjunct for PHPT subtype differentiation and as a predictor of skeletal health. Its ability to identify normocalcemic PHPT cases, which often go undiagnosed due to normal serum calcium, highlights its clinical utility. The Cl/Mg ratio, while not useful for subtype differentiation, emerged as a valuable marker for nephrolithiasis risk assessment, reinforcing the role of chloride metabolism in PHPT complications.

Conclusion: Cl/P and Cl/Mg ratios are promising, cost-effective biomarkers for PHPT diagnosis and risk stratification. Their integration into clinical practice may enhance diagnostic precision and aid in early intervention strategies. Further multicenter studies are needed to validate these findings and establish standardized cut-off values.