The aim of this study was to investigate the skeletal muscle sodium/potassium (Na/K) ratio in acromegaly before and 1 year after trans-sphenoidal removal of a growth hormone (GH)-secreting pituitary adenoma. Muscle biopsies were taken and skeletal muscle electrolytes, body composition, glucose, insulin and blood pressure were studied. Fasting blood glucose and plasma insulin levels, but not blood pressure, were higher in acromegalic patients (N = 9) than in controls (N = 6). The skeletal 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 untreated patients with acromegaly as compared to weight-matched healthy controls. Elevated GH, glucose and insulin levels normalized after surgery. Blood pressure remained unchanged. The total body potassium content, the lean body mass and the total body water content decreased and 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 skeletal 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 higher 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 the Na/K pump after successful trans-sphenoidal surgery in acromegaly.
Kerstin Landin, Björn Petruson, Karl-Erik Jakobsson and Bengt-Åke Bengtsson
Staffan Edén, Bengt-Åke Bengtsson, Kerstin Albertsson-Wikland, Jörgen Elfversson, Göran Lindstedt, Per-Arne Lundberg, Björn Petruson and Sten Rosberg
Abstract. Profiles of plasma GH, plasma somatomedin-C and serum PRL concentrations as well as serum GH response to iv TRH were determined in 11 patients with acromegaly before and 10 days after surgery. Blood for profile determinations was drawn from a peripheral vein with a continuous withdrawal pump changing the recipient tube at 30-min intervals. Before surgery all patients had high plasma GH concentrations with irregular peaks and somatomedin-C concentrations were elevated. The response to TRH was abnormal in 8 patients. Three patients had slightly elevated PRL concentrations and one had high PRL concentration (6900 mU/l). Ten days after surgery GH concentrations were still high in 2 patients (>5 mU/l), as were somatomedin-C concentrations (3.2 and 2.4 U/l, respectively). In 3 patients basal GH concentrations were <5 mU/l and somatomedin-C concentrations were normal, but there were no major peaks in plasma GH concentrations. In 2 patients major peaks in GH concentrations appeared after surgery, but basal GH concentrations were 1.9 and 0.95 mU/l, respectively. One patient with hyperprolactinemia still had slightly elevated PRL concentration (486 mU/l), but the response to TRH was normalized. Finally, in 4 patients, mean GH concentrations were markedly reduced, somatomedin-C concentrations normalized and apparently normal plasma GH profiles appeared with low or undetectable basal levels separating major peaks. The results indicate that in some patients with acromegaly apparently normal GH secretion can be demonstrated 10 days postoperatively. Characterization of circadian GH rhythms during the early postoperative stage may contribute to the evaluation of the effect of surgery.