A 49 year old lady was referred to the endocrine clinic for investigation of intermittent hyponatremia. She had two admissions in the year with lower abdominal, back pain and dark urine and treated for urinary infections.Serum sodium was 112,114 millimoles per litre, which responded to fluid restriction.
She had a past history of syncopal episodes, hypertension treated with atenolol, amlodipine. She was a nonsmoker, alcohol intake was 14 units per week.
BP was 140/85, no postural drop. Systemic examination was normal. Previous investigations included short synacthen test (peak cortisol 1426 nanomoles per litre), normal thyroid function. CT thorax, ultrasound abdomen, gastroscopy, echocardiogram, lateral skull x-ray were normal.
Review of history revealed close correlation between abdominal pain and hyponatremia. Investigations during hyponatremia suggested SIADH (plasma and urine osmolality of 244, 400 respectively). Further investigations revealed intact Pituitary-gonadotroph axis. Porphyria screen was positive and results were conclusive of acute intermittent porphyria. The patient has been informed about the diagnosis, likely precipitating causes and has been referred to the genetic clinic. She has had no further admissions with hyponatremia.
Although hyponatremia has been associated with acute porphyria, it is not a usual feature leading to the diagnosis and such profound hyponatremia is uncommon.
Conclusion : Endocrinologists are often referred patients with hyponatremia. A careful history including drug intake is vital in evaluating a patient. A diagnosis of SIADH should always be followed by tests to look at underlying cause. Malignancy, infection, drugs seem to be commonly looked for, however, it is important to look for metabolic causes as well.
22 - 24 Mar 2004
British Endocrine Societies