Endocrine Abstracts

Introduction: Adipsic arginine vasopressin deficiency (AAVP-D) is rare, accounting for ~100 cases in literature. It poses multiple therapeutic challenges, with increased morbidity and mortality. We discuss an interesting case of AAVP-D, and the importance of careful management and follow-up.

Presentation: 24-year-old female underwent debulking of recurrent central neurocytoma. Post-operatively, she developed new confusion with hypernatraemia (171 mmol/l) and increased urine output (~354mls/h). Plasma osmolality was raised (346 mmol/kg), with low urine osmolality (142 mmol/kg) and adipsia. Transient AAVP-D was suspected; successfully treated with IV Desmopressin. Her symptomatic hypernatraemia resolved (133 mmol/l), and she was discharged. One week later, she re-presented with worsening confusion and agitation. Admission bloods showed hypernatraemia (170 mmol/l), raised osmolality (329 mmol/kg), acute kidney injury (urea 10.0 mmol/l, creatinine 104 micromol/l), alongside increased urinary frequency (80-355mls/h). Permanent AAVP-D was suspected; regular Desmopressin 50 micrograms/day was thus commenced. Desmopressin has since been titrated according to plasma sodium levels (currently 150 micrograms/day) in outpatient Endocrinology clinic, alongside fixed oral fluid intake of 2L/day.

Discussion: AAVP-D poses multiple clinical challenges. Thirst sensation secondary to increased osmolality is lost, complicated by confusion associated with hypernatraemia. Variations in fluid intake can result in catastrophic fluctuations in sodium and osmolality levels. Management thus includes calculating a fixed fluid goal daily and titration with desmopressin to ensure consistent urine output, patient weight, and plasma sodium level. Historically morbidity was associated with confusion regarding previous nomenclature of ‘diabetes insipidus’; mistaken for more common ‘diabetes mellitus’. Change in nomenclature to ‘arginine vasopressin deficiency’ in 2022, allows further clarification on pathophysiology of this complex disease.

Conclusion: AAVP-D is a rare clinical dilemma. We wish to highlight from our patient’s case the pathophysiology of AAVP-D, and the importance of careful fluid balance and medical management, and emphasise why alternative nomenclature was necessary.