Hyponatraemia in older people as a sign of adrenal insufficiency: a case-control study.
BACKGROUND
Hyponatraemia is a common cause of hospitalisation in older adults. Adrenal insufficiency (AI) can result in hyponatraemia.


OBJECTIVE
The aim of our study was to determine the frequency and characteristics of AI in elderly patients with hyponatraemia.


METHODS
Thirty patients ≥65 years with Na(+) ≤130 mmol/L and 30 age-matched control subjects, all hospitalised, were included in the study. Plasma cortisol levels were determined before and after intravenous administration of 1 µg synthetic adrenocorticotropin hormone. A peak cortisol >550 nmol/L was considered to exclude AI.


RESULTS
Sodium levels were 125 ± 5 and 139.8 ± 2 mmol/L in the hyponatremic and control groups respectively. Baseline cortisol <550 nmol/L was found in a half of hyponatremic patients. However, stimulated cortisol levels were compatible with AI in only one case (3%) and none of the controls. The mean cortisol levels were significantly higher in hyponatremic compared with control subjects, both in the basal state (585 ± 215 and 381 ± 135 nmol/L, respectively, P < 0.001) and after stimulation (933 ± 254 and 781 ± 160 nmol/L, P < 0.05). However, the incremental increase in cortisol levels after stimulation was similar in the two groups (361 ± 196 and 403 ± 155 nmol/L) CONCLUSIONS: AI is an uncommon cause of hyponatraemia in older age. Based on this small cohort, AI may be present in 3% of elderly patients with hyponatraemia. AI cannot be excluded by baseline cortisol in a significant minority of hyponatremic patients and further testing with adrenocorticotropin hormone stimulation is needed.
Winchester Behr
T
T
Maccabi Healthcare Services and Departments of              Geriatric Medicine and              Internal Medicine, Shaare Zedek Medical Center, Jerusalem, Israel.
Sonnenblick
M
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Nesher
G
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Munter
G
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D000309:Adrenal Insufficiency / Q000150:complications / Q000175:diagnosis*; D000324:Adrenocorticotropic Hormone; D000368:Aged; D002318:Cardiovascular Diseases / Q000453:epidemiology; D016022:Case-Control Studies; D002561:Cerebrovascular Disorders / Q000453:epidemiology; D005260:Female; D005767:Gastrointestinal Diseases / Q000453:epidemiology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism; D007010:Hyponatremia / Q000209:etiology*; D007297:Inpatients; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects; D012964:Sodium / Q000097:blood; D049993:Sodium Chloride Symporter Inhibitors / Q000009:adverse effects
D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone; D011188:Potassium; D017367:Selective Serotonin Reuptake Inhibitors; D012964:Sodium; D049993:Sodium Chloride Symporter Inhibitors