Endocrine Abstracts

Introduction: According to recent studies, fluid and electrolyte disturbances complicate the course of transnasal adenomectomy for pituitary adenomas in 13–30% of cases and are associated with a high risk of neurological complications and increased mortality. Neuropeptides discovered in recent decades (apelin, copeptin, oxytocin, brain natriuretic peptide) in many studies demonstrate their significant effect on the regulation of water-electrolyte metabolism, which makes them potentially important hormonal markers of its complications.

Aim: To study a neuroendocrine regulation of water and electrolyte metabolism in patients after transnasal adenomectomy and in cases of the development of hyponatremia.

Materials and methods: The study included the results of dynamic control of sodium and neuropeptides in 22 patients who underwent pituitary adenoma removal (inactive pituitary adenoma – 8 patients, acromegaly – 8 patients, Cushing’s disease – 6 patients, 6 men and 16 women, median age 52 years [Q25 39; Q75 62]), 10 of whom developed hyponatremia (group 1) with a median serum sodium of 125 mmol/l, and 12 had no water–electrolyte disorders (group 2). In all patients, Na was determined in blood serum, as well as by ELISA apelin 12, copeptin, oxytocin and proBNP in plasma 24 h before surgery, 12–24 h, 3, 5 and 7–8 days after surgery.

Results: The analysis showed significant changes in oxytocin levels without significant changes in concentrations of other neuropeptides in hyponatremia. Spearman correlation analysis of simultaneous concentrations of oxytocin and sodium in the blood showed the presence of an association between the parameters in the postoperative period, which were manifested by the appearance of a positive correlation on day 3, and a negative correlation on days 5 and 7–8. When comparing oxytocin levels in the groups of hyponatremia and the absence of water–electrolyte disorders, statistically significant differences were revealed. The median concentration of this hormone in the hyponatremia group on day 7–8 was 2.1 times higher with hyponatremia – 6781 vs 3.199 ng/ml for the hyponatremia group and control, respectively (P=0.002 for the Mann–Whitney U-test)

Conclusions: Transnasal adenomectomy is the cause of severe hyponatremia in 7–18% of cases, in the pathogenesis of which, apparently, copeptin and oxytocin play a leading role, and the secretion of which has the character of inadequately elevated levels with the loss of a negative feedback with the concentration of sodium in the blood. At the same time, oxytocin has the potential to be a hormonal marker of this life-threatening complication.