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.