Endocrine Abstracts

Background: Hyponatremia is a common electrolyte abnormality, especially in elderly, hospitalized patients, with a prevalence of severe hyponatremia (<125 mmol/l) up to 6–8%. Pituitary insufficiency (TSH+ACTH) may be difficult to diagnose, but it is important to differentiate it from SIADH and cerebral salt wasting syndrome.

Aim: To describe the aetiology and outcome of patients with hyponatremia due to pituitary insufficiency in a tertiary endocrine center.

Patients and methods: The records of 40 patients presented with/referred for hyponatremia (<130 mmol/l) in the Department of Pituitary Pathology between 2005 and 2012, were retrospectively reviewed. There were identified 30 patients (16M/14F, aged 61.9±14.3 years) with hyponatremia due to pituitary insufficiency, three patients with severe primary hypothyroidism and seven patients with primary adrenal failure.

Results: In 13 patients, hyponatremia was the event revealing pituitary insufficiency; mean serum sodium at diagnosis was 113.7±8.6 mmol/l (range: 97–128). Severe hyponatremia (<125 mmol/l) was recorded in 26/30 patients (86.7%). Panhypopituitarism or multiple pituitary deficiencies were present in 28 out of 30 patients (93.3%); two patients (6.7%) showed isolated ACTH deficiency. Median 0800 h serum cortisol at the moment of diagnosis of secondary adrenal failure was 2.3 μg/dl (range: nd-12.34 μg/dl). The etiology of panhypopituitarism was: pituitary tumors (n=18), empty sella (n=5), Sheehan’s syndrome (n=4 cases), possible autoimmune hypophysitis (n=3). There were 14 nonfunctioning pituitary adenomas, 1 acromegaly, 2 prolactinomas and 1 ACTH secreting adenoma. On first hospital admission, 5/30 patients were comatose and two patients had seizures. All patients recovered after saline infusion and steroid therapy; three patients were cautiously treated with infusions of 5.85% saline diluted in 0.9% saline. There were no fatalities or osmotic demyelization syndrome.

Conclusions: Hypopituitarism with TSH and ACTH insufficiency seems to be a frequent endocrine cause of severe hyponatremia. Correct diagnosis is important, as glucocorticoids are very effective.