Muscle Function Improves After Parathyroidectomy: Role of Calcium Reduction Over PTH Decline

Purpose: Primary hyperparathyroidism (PHPT) has been associated with subclinical neuromuscular dysfunction; however, the clinical correlates of muscle strength and morphology in PHPT remain undercharacterized. We hypothesized that muscle dysfunction in PHPT is reversible after parathyroidectomy and that the reduction in serum calcium predicts early postoperative improvement. Design: A prospective observational study conducted at a tertiary care center Methods: Fifty-three PHPT patients and 53 age-, sex-, and BMI-matched healthy controls were assessed using handgrip strength tests (HGS), 4-meter walking speed (4MGS), the timed-up-and-go (TUG) test, and the 5-time sit-to-stand test (5XSTS). Muscle thickness was measured via ultrasonography and body composition by bioelectrical impedance analysis (BIA). Surgical indications were based on international guidelines for classical PHPT and on clinical judgment in selected normocalcemic cases. Thirty-four patients underwent PTX and were re-evaluated three months postoperatively. Generalized Linear Mixed Models (GLMM) were used to identify predictors of changes in muscle function. Results: At baseline, patients with PHPT demonstrated significantly reduced HGS, prolonged durations in the TUG and 5XSTS tests, and decreased gastrocnemius muscle (GM) thickness compared to healthy controls (p < 0.05). Following PTX, both GM thickness and lower limb functional performance (TUG, 5XSTS) improved significantly. GLMM analysis identified reductions in serum calcium as independent predictors of functional improvement. Vitamin D status was standardized across all participants to minimize confounding and enhance internal validity. Conclusion: Parathyroidectomy in PHPT patients leads to early improvements in muscle thickness and lower extremity function, suggesting a multimodal recovery process; whether assessment enhances surgical decision-making and patient selection needs to be explored in further studies.