Association of Biochemical Indices with Skeletal Involvement in Primary Hyperparathyroidism

Objective: Primary hyperparathyroidism (PHPT) is frequently associated with osteoporosis and cortical bone loss. This study aimed to investigate associations of
biochemical parameters, adenoma size, the parathyroid function index (PFI), and the Wisconsin index (WIN) with osteoporosis and cortical skeletal involvement in
patients with PHPT.
Materials and Methods: This retrospective study included 269 patients with PHPT. Participants were grouped by osteoporosis status. Demographic, biochemical, and
densitometric data, along with PFI and WIN, were assessed. Among patients with osteoporosis, associations between distal one-third radius T-scores and biochemical
parameters, composite indices, and adenoma size were examined. ROC analysis evaluated the ability of alkaline phosphatase (ALP), PTH, PFI, and WIN to distinguish
osteoporosis.
Results: Osteoporosis was identified in 124 patients (46.1%). Patients with osteoporosis were older than those without osteoporosis (p<0.001). ALP levels were higher
(p<0.001), whereas PTH levels showed a borderline increase (p=0.050). Distal one-third radius T-scores were inversely associated with serum calcium (Ca), PTH, ALP,
PFI, and WIN (all p≤0.005). The receiver operating characteristic (ROC) analysis showed that ALP had modest discriminative performance for osteoporosis [area under
the curve (AUC)=0.674, p<0.001]. In contrast, PTH, PFI, and WIN showed no meaningful discriminative ability.
Conclusion: Osteoporosis was common in PHPT and associated with older age, higher ALP levels, and borderline-high PTH concentrations. PFI and WIN were associated
with cortical bone loss but had limited utility for identifying osteoporosis, whereas ALP showed the highest, albeit modest, discriminatory performance among the
evaluated parameters.