Endocrine Abstracts

Hyponatraemia is the most commonly encountered electrolyte disturbance seen in 15-20% of inpatients. Regardless of severity, hyponatraemia is associated with increased length of stay, morbidity and mortality. We describe a case of a 60-year-old patient admitted with recurrent falls, head injury and hyponatraemia on a background of young-onset Parkinson’s disease with predominant cognitive decline, bladder disturbances and autonomic failure. Following multiple treatments for nocturnal enuresis and her decline for urinary catheter, Desmopressin was introduced by uro-neurology to avert sleep disturbance and to mitigate risks associated with mobilisation at night. Previously she has had multiple admissions and frequent sodium checks in tertiary and primary care with reassuring sodium levels. As such the dose of sublingual desmopressin was increased from 60 mg to 120 mg a few months before admission. At presentation her serum sodium was 120 mmol/l. Desmopressin remained on regular prescription until review by endocrinology where it was stopped and fluid restriction commenced. Her thyroid function test and 9am cortisol were within normal range. Her serum sodium level slowly incremented to 134 mmol/l over 5 days. As a result, nocturnal polyuria and postural hypotension worsened with cessation of desmopressin and fluid restriction respectively. Due to the complexity of her neurological condition, her management received multidisciplinary input from the autonomic failure and uro-neurology specialists. It was extremely challenging to achieve a delicate balance between normal serum sodium levels whilst simultaneously addressing frequent nocturia and postural disturbances with fluid restriction and desmopressin titration. This will be an ongoing challenge in the foreseeable future given her progressive neurological symptoms and autonomic failure. This case aims to raise awareness regarding the increased prevalence of desmopressin use outside of endocrinology, the challenges faced in the management of hyponatraemia and considerations needed when making medication changes taking into account the clinical context.