Endocrine Abstracts

Introduction: Patients with primary hyperparathyroidism (PHPT) present high calcium and PTH levels while some patients present also high PTH levels but normal calcium levels (NHPT) and such patients be considered as having normocalcemic hyperparathyroidism. On the other hand vitamin D deficient patients develop secondary hyperparathyroidism (SHPT). Sometimes normocalcemic- and secondary hyperparathyroidism coexist. Therefore in clinical settings it is very difficult to distinguish primary hyperparathyroidism and normocalcemic hyperparathyroidism from secondary hyperparathyroidism.

Aim: The aim of our case control study is to differentiate these entities using the parathyroid functional index (PFI=PTH × Ca devided by P) and the Wisconsin Index (WI=PTH × Ca).

Patients and Methods: Twenty seven patients with PHP, 15 patients with NPHPT, 38 patients with SHPT and 47 apparently healthy (NC) were included. All patients had normal renal function. In all participants serum calcium, phosphorus, PTH and albumin were measured and corrected calcium, PFI and WI were evaluated.

Results: The PHPT group had the highest PFI compared to NHPT group (P=0.02) and also to the other two groups (SHPT and NC, all P<0.0001). The WI was higher in the PHPT group compared to SHPT group (P<0.0001) and to NC group (P<0.0001). WI was also higher in the NPHPT group compared to NC group (P<0.0001). In the healthy individuals (NC group) the highest values of PFI (18.41) and of WI (20.81) were taken as cut-off values and based on this sensitivity and specificity of the two indexes were evaluated and are presented in the following table.

Conclusion: PFI and WI can be useful in the differential diagnosis of hyperparathyroidism. It seems that the PFI performs slightly better than the WI in distinguishing patients with PHPT and NHPT from healthy individuals, whereas the WI distinguishes only patients with PHPT from healthy individuals.