Endocrine Abstracts

Arginine Vasopressin Deficiency (AVP-D) a rare endocrine disorder has a reported prevalence of 1 in 25,000 individuals. Central AVP-D is the most common form resulting from deficiency of the hormone AVP secreted from posterior pituitary gland. In the case of desmopressin-associated hyponatremia, majority of surveyed endocrine registrar trainees favour its cessation (67%), which may lead to serious consequences. Can using reverse osmolality theory assist in the management decision-making? A 27-year-old man was admitted in A&E unit with 2-day history of new onset headache, poor concentration, leg cramps and vomiting. He was diagnosed with partial central AVP-D as a 10-year-old, treated with desmopressin but lost to follow up at 18-years old. He had recently been active in a gym and started to drink 4 litres of water with high protein diet as part of his fitness regimen. On examination, he was normotensive, euvolemic with normal neurological and systemic examination. Initial serum sodium was 117. Random serum cortisol was 22 nmol/l but had adequate short Synacthen test result. The rest of his anterior pituitary hormone panel was unremarkable. Desmopressin was initially withheld by admitting doctor and he developed polyuria (>5L over 24-hours). Due to his symptomatic acute hyponatraemia, a single dose of hypertonic saline (2.7% 150 ml in 30 minutes) was given with close monitoring of fluid balance. Repeat sodium increased rapidly to 127 mmol/mol within 2 hours and Dextrose5% water infusion was given together with desmopressin. His urine osmolality after hypertonic saline showed a reversed urine osmolality pattern. There was a resolution of symptoms and biochemical parameters upon discharge. Learning points: 1. Theory of using reverse urine osmolality pattern in predicting patients at risk of osmotic diuresis and need for desmopressin continuation. 2. Hypertonic saline remains the recommended treatment option in patients with severe symptomatic hyponatraemia with continuation of desmopressin.