Muscle Function Improves After Parathyroidectomy: The Role of Calcium Reduction Over Parathyroid Hormone Decline

PURPOSE: Primary hyperparathyroidism 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 primary hyperparathyroidism is reversible after parathyroidectomy and that the reduction in serum calcium predicts early postoperative improvement.

DESIGN: Prospective observational study conducted at a tertiary care center.

METHODS: Fifty-three primary hyperparathyroidism patients and 53 age-, sex-, and body mass index-matched healthy controls were assessed using handgrip strength tests, 4-m walking speed, the timed-up-and-go test, and the five-time sit-to-stand test. The muscle thickness was measured via ultrasonography and body composition by bioelectrical impedance analysis. Surgical indications were based on international guidelines for classical primary hyperparathyroidism and on clinical judgment in selected normocalcemic cases. Thirty-four patients underwent parathyroidectomy and were re-evaluated 3 months postoperatively. Generalized linear mixed models were used to identify predictors of changes in muscle function.

RESULTS: At baseline, patients with primary hyperparathyroidism demonstrated significantly reduced handgrip strength, prolonged durations in the timed-up-and-go and five-time sit-to-stand test tests, and decreased gastrocnemius muscle thickness compared to healthy controls (p<0.05). Following parathyroidectomy, both gastrocnemius muscle thickness and lower limb functional performance (timed-up-and-go and five-time sit-to-stand test) improved significantly. Generalized linear mixed model 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.

CONCLUSIONS: Parathyroidectomy in primary hyperparathyroidism 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.