SKELETAL-MUSCLE SODIUM AND POTASSIUM CHANGES AFTER SUCCESSFUL SURGERYIN ACROMEGALY - RELATION TO BODY-COMPOSITION, BLOOD-GLUCOSE, PLASMA-INSULIN AND BLOOD-PRESSURE

The aim of this study was to investigate the skeletal muscle sodium/po tassium (Na/K) ratio in acromegaly before and 1 year after trans-sphen oidal removal of a growth hormone (GH)-secreting pituitary adenoma. Mu scle biopsies were taken and skeletal muscle electrolytes, body compos ition, glucose, insulin and blood pressure were studied. Fasting blood glucose and plasma insulin levels, but not blood pressure, were highe r in acromegatic patients (N = 9) than in controls (N = 6). The skelet al muscle potassium content was higher (p<0.01) but the sodium content and the Na/K ratio were lower (p<0.05 and p<0.001, respectively) in u ntreated patients with acromegaly as compared to weight-matched health y controls. Elevated GH, glucose and insulin levels normalized after s urgery. Blood pressure remained unchanged. The total body potassium co ntent, the lean body mass and the total body water content decreased a nd the body fat content increased while the body weight was unchanged. The skeletal muscle potassium content decreased from median (range)! 9.8 (9.2-11.5) to 7.7 (5.7-9.5) mmol/100 g wet wt (p<0.001). The skel etal muscle sodium content increased from 2.8 (2.5-3.9) to 5.1 (4.3-6. 7) mmol/100 g wet wt (p<0.001) and the Na/K ratio increased from 0.28 (0.26-0.38) to 0.56 (0.51-1.18) (p<0.001) after surgery, which is a hi gher level than the controls with a Na/K ratio of 0.47 (0.39-0.84) (p< 0.01). These changes seem to be mediated by a decreased GH effect on t he Na/K pump after successful trans-sphenoidal surgery in acromegaly.