Gymnastik- och idrottshögskolan, GIH

Context Primary hyperparathyroidism leads to hypercalcemia and muscle dysfunction. Muscle weakness is associated with increased morbidity and mortality but is overlooked in surgical treatment guidelines. While parathyroidectomy is the only curative treatment, its effects on skeletal muscle strength and molecular remodeling remain underexplored. Objective Determining functional and molecular changes in skeletal muscle before and after parathyroidectomy. Methods A prospective observational study was conducted in the spring and fall of 2023. Patients underwent surgery at the Endocrine and Sarcoma unit at the Karolinska University Hospital in Stockholm, Sweden. A total of 21 postmenopausal women with primary hyperparathyroidism planned for surgery were included, whereof 15 completed the study protocol. Participants had no disabling comorbidities. Muscle function tests, muscle biopsies, MRI, and biochemical panels were analyzed before and after parathyroidectomy. Muscle composition of m. vastus lateralis was tested with MRI and transcriptomic analysis of muscle biopsies. Leg strength was evaluated with timed stands test and peak torque tests. Activity level was estimated from questionnaires. Results Parathyroidectomy normalized calcium levels (P < .001) and improved muscle strength (P < .005). Muscle volume increased (P = .023) and fat fraction was reduced (P = .013), without changes in physical activity levels. Transcriptomic analysis identified 981 differentially expressed genes postsurgery, enriched in pathways mirroring exercise-induced adaptations. Conclusion These findings highlight the impact of parathyroidectomy on skeletal muscle function and suggest that muscle assessments should be included in surgical referral criteria to address age-related muscle decline and improve long-term outcomes.