Muscle structure and function before and after surgery for primary hyperparathyroidism

In 23 unselected cases of primary hyperparathyroidism (pHPT), muscle strength, morphology and enzymatic activities were studied and electromyography (EMG) performed before and 6 months after surgical treatment. Hypercalcemia was mostly mild or moderate. Nine women undergoing surgery for benign thyroid conditions served as controls regarding muscle strength, while muscle morphologic and enzymatic data were compared with findings in healthy persons of similar age. Only three pHPT patients reported muscle weakness preoperatively, and two were subjectively improved after surgery. Muscle strength did not differ significantly before or after operation between patients and controls: After surgery both groups showed increased isokinetic muscle strength at higher angular velocities. Nor did muscle morphology differ between pHPT patients and controls. No conclusive EMG changes were found before or after surgery for pHPT but postoperatively the pHPT patients showed significant increase in glycolytic but not oxidative muscle enzymes, possibly reflecting early effect of pHPT on especially type II fibers, which previously were shown to be most extensively involved in pHPT. Otherwise no measurable negative effects of mild or moderate pHPT were found on muscle strength or function.