Muscular performance and fatigue in primary hyperparathyroidism

The purpose of this study was to evaluate changes in muscular strength and endurance, work capacity, and subjective fatigue following surgical treatme nt of primary hyperparathyroidism (pHPT), and to assess whether changes in muscular function were due to changes in activation of the muscles. A prosp ective consecutive study design was used, and patients surgically treated f or nontoxic goiter sen ed as controls. Nineteen female patients with mild t o moderate pHPT and 20 controls were included. Maximal isometric handgrip a nd quadriceps strength, quadriceps endurance (intermittent stimulation), an d quadriceps activation (superimposed twitch technique) were used for evalu ation of muscular function. All patients were operated on successfully. Kne e extension strength increased by 17 +/- 17% (mean +/- SD;p = 0.0001) in th e patients, whereas no change was observed in the controls. The relative st rength increase correlated positively to patient age at operation (r = 0.52 , p = 0.02). Handgrip strength, quadriceps endurance, and general work capa city did not change in any group after operation. Subjective fatigue was pr eoperatively higher in patients than in controls (p = 0.01), and decreased postoperatively to the level of controls. In conclusion, women with pHPT in crease knee extension force after parathyroidectomy as a result of increase d force generation capacity of the muscle. If change in physical performanc e is a determinant for change in subjective fatigue in pHPT after operation , then change in strength of the quadriceps muscle seems to be of primary i mportance, whereas handgrip strength, muscular endurance, and work capacity do not seem to be important. The cause of the increasing strength benefit with increasing age at operation as found in this study needs further inves tigation.