Poster 18 - Sofia Björnsdotter Öberg, Endocrine Surgery

Summary

Introduction

Patients with primary hyperparathyroidism often complain of skeletal muscle weakness. Previous studies from our group have shown that proximal muscle strength performance improves after parathyroidectomy measured by timed stand test (TST) where the patient rises from a chair ten times as fast as possible. We study changes in skeletal muscle RNA expression after parathyroidectomy to unravel the mechanism behind muscle strength improvement. 

Materials and Methods

21 women with pHPT, planned for surgery, were included in the study. Only postmenopausal women were included to control for hormonal differences. Muscle strength tests were performed, before and three months after surgery. MRI scans were done to study muscle volume and compositional changes after surgery. A muscle biopsy from m. vastus lateralis was taken before and three months after surgery, RNA was extracted and sent for sequencing. The changes before and after surgery were analysed with Wilcoxon signed rank test (non-normally distributed data). 

Results

All patients had histologically proven parathyroid adenomas and were normalised in ionised calcium and phosphate after surgery. All patients followed up (n=17) improved significantly in muscle strength three months after parathyroidectomy. The TST mean time was reduced by 6 seconds (26±9 to 20±6 sec mean+SD, p<0.0001). Biodex isokinetic muscle strength, measuring peak torque (Nm) of the quadriceps and hamstrings at three different speeds (degrees per second), were all significantly increased (p<0.0001). Preliminary data from the RNA sequencing revealed changes in RNA expression of genes involved in mitochondrial function and skeletal muscle remodelling. 

Conclusion

Skeletal muscle strength improves after parathyroidectomy in patients with primary hyperparathyroidism, which is important to recognise in the decision about surgery, especially in the elderly, frail population. The expression of genes responsible for mitochondrial function and skeletal muscle remodelling are changed in muscle biopsies after surgery, and could explain the increase in skeletal muscle strength.