title: Maintained serum sodium in male ultra-marathoners--the role of fluid intake, vasopressin, and aldosterone in fluid and electrolyte regulation.
abstract: Exercise-associated hyponatremia (EAH) is a well know electrolyte disorder in endurance athletes. Although fluid overload is the most like etiology, recent studies, however, argued whether EAH is a disorder of vasopressin secretion. The aims of the present study were to investigate (i) the prevalence of EAH in male ultra-marathoners and (ii) whether fluid intake, aldosterone or vasopressin, as measured by copeptin, were associated with post-race serum sodium concentration ([Na+]). In 50 male ultra-marathoners in a 100 km ultra-marathon, serum [Na+], aldosterone, copeptin, serum and urine osmolality, and body mass were measured pre- and post-race. Fluid intake, renal function parameters and urine excretion were measured. No athlete developed EAH. Copeptin and aldosterone increased; a significant correlation was found between the change in copeptin and the change in serum [Na+], no correlation was found between aldosterone and serum [Na+]. Serum [Na+] increased by 1.6%; body mass decreased by 1.9 kg. The change in serum [Na+] and body mass correlated significantly and negatively. The fluid intake of ~ 0.58 l/h was positively related to the change in body mass and negatively to both post-race serum [Na+] and the change in serum [Na+]. We conclude that serum [Na+] was maintained by both the mechanisms of fluid intake and the hormonal regulation of vasopressin.
authors.affiliation: Institute of General Practice and Health Services Research, University of Zurich, Zurich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Bürge
authors.forename: B
authors.initials: B
authors.lastname: Knechtle
authors.forename: P
authors.initials: P
authors.lastname: Knechtle
authors.forename: M
authors.initials: M
authors.lastname: Gnädinger
authors.forename: C A
authors.initials: CA
authors.lastname: Rüst
authors.forename: A C
authors.initials: AC
authors.lastname: Rüst
authors.forename: T
authors.initials: T
authors.lastname: Rosemann
mesh_terms: D000450:Aldosterone / Q000097:blood / Q000378:metabolism*; D056352:Athletes; D004326:Drinking; D004573:Electrolytes / Q000378:metabolism*; D006801:Humans; D007010:Hyponatremia / Q000453:epidemiology / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012420:Running / Q000502:physiology*; D012964:Sodium / Q000097:blood*; D014667:Vasopressins / Q000097:blood / Q000378:metabolism*
chemical_list: D004573:Electrolytes; D014667:Vasopressins; D000450:Aldosterone; D012964:Sodium