Calcium/phosphate ratio: an additional tool for the clinical management of asymptomatic primary hyperparathyroidism?

Purpose Serum calcium/phosphate ratio (Ca/P) has been recently proposed as an additional tool to identify primary hyperparathyroidism (PHPT), especially in patients with subclinical presentation, with a proposed cut-off of 3.3 when both values are expressed in mg/dL. No data are available on the relationship between Ca/P and the clinical presentation of PHPT. We thus evaluated this relationship in a large, single-center, unselected series.Methods515 consecutive PHPT patients (mean age 65 +/- 13.15 years, 77.1% females) were retrospectively evaluated at diagnosis.Results Mean Ca/P was 4.54 +/- 1.5 (range 2.36-13.9), being higher than 3.3 in 88.5% of patients. Ca/P was significantly higher in (1) males, (2) symptomatic PHPT, (3) patients with 25-hydroxy vitamin D levels lower than 20 mu g/L, (4) patients with osteitis fibrosa cystica, (5) patients with T score < - 2.5 at the radial site. In a multivariate regression analysis, Ca/P resulted significantly associated with PTH levels. After the exclusion of 57 patients with asymptomatic PHPT (aPHPT) patients and serum Ca higher than 1 mg/dL above the upper limit of normal range, no differences were found in Ca/P between aPHPT meeting or not surgical criteria.Conclusions In PHPT Ca/P ratio is associated with increased biochemical and clinical severity of disease and represents a direct indicator of clinical bone damage. However, it does not seem an additional tool to identify aPHPT patients reaching surgical indication.

Automated summary

This study evaluated the relationship between serum calcium/phosphate ratio (Ca/P) and the clinical presentation of primary hyperparathyroidism (PHPT). The results showed that Ca/P ratio is associated with the clinical and biochemical severity of the disease, but is not an additional tool to identify asymptomatic PHPT patients reaching surgical indication.