The contribution of undiagnosed adrenal insufficiency to euvolaemic hyponatraemia: results of a large prospective single-centre study.
OBJECTIVE
The syndrome of inappropriate antidiuresis (SIAD) is the commonest cause of hyponatraemia. Data on SIAD are mainly derived from retrospective studies, often with poor ascertainment of the minimum criteria for the correct diagnosis. Reliable data on the incidence of adrenal failure in SIAD are therefore unavailable. The aim of the study was to describe the aetiology of SIAD and in particular to define the prevalence of undiagnosed adrenal insufficiency.


METHODS
Prospective, single centre, noninterventional, observational study of patients admitted to Beaumont Hospital with euvolaemic hyponatraemia (plasma sodium ≤ 130 mmol/l) between January 1st and October 1st 2015.


METHODS
A total of 1323 admissions with hyponatraemia were prospectively evaluated; 576 had euvolaemic hyponatraemia, with 573 (43·4%) initially classified as SIAD.


METHODS
(i) Aetiology of SIAD, defined by diagnostic criteria; (ii) Incidence of adrenal insufficiency.


RESULTS
Central nervous system diseases were the commonest cause of SIAD (n = 148, 26%) followed by pulmonary diseases (n = 111, 19%), malignancy (n = 105, 18%) and drugs (n = 47, 8%). A total of 22 patients (3·8%), initially diagnosed as SIAD, were reclassified as secondary adrenal insufficiency on the basis of cortisol measurements and clinical presentation; 9/22 cases had undiagnosed hypopituitarism; 13/22 patients had secondary adrenal insufficiency due to exogenous steroid administration.


CONCLUSIONS
In a large, prospective and well-defined cohort of euvolaemic hyponatraemia, undiagnosed secondary adrenal insufficiency co-occurred in 3·8% of cases initially diagnosed as SIAD. Undiagnosed pituitary disease was responsible for 1·5% of cases presenting as euvolaemic hyponatraemia.
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Martín
M
Cuesta
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Aoife
A
Garrahy
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
David
D
Slattery
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Saket
S
Gupta
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Anne Marie
AM
Hannon
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Hannah
H
Forde
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Karen
K
McGurren
Department of Endocrinology, The Adelaide and Meath Hospital, Dublin/Trinity College, Dublin, Ireland.
Mark
M
Sherlock
Department of Chemical Pathology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
William
W
Tormey
Academic Department of Endocrinology, Beaumont Hospital/RCSI Medical School, Dublin, Ireland.
Christopher J
CJ
Thompson
D000309:Adrenal Insufficiency / Q000150:complications* / Q000175:diagnosis; D000368:Aged; D000369:Aged, 80 and over; D002493:Central Nervous System Diseases / Q000150:complications; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000209:etiology*; D007177:Inappropriate ADH Syndrome / Q000150:complications* / Q000175:diagnosis / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications; D010900:Pituitary Diseases / Q000150:complications; D011446:Prospective Studies