Endocrine Abstracts

JOINT3581

Introduction: Arginine vasopressin deficiency (AVP-D), formerly central diabetes insipidus, results from inadequate production of arginine vasopressin (AVP), also called antidiuretic hormone (ADH). It can be congenital or acquired, often resulting from tumours affecting the hypothalamic-pituitary region. The condition is marked by excessive urine output (polyuria), usually offset by increased water intake. Adipsic arginine vasopressin deficiency (AAVP-D), a rare form affecting hypothalamic osmoreceptors, impairs thirst perception, leading to an increased risk of dehydration and hypernatremia. This study retrospectively analyses patients with AAVP-D among those diagnosed with central nervous system (CNS) tumours in our centre.

Cases: Among 383 paediatric patients with CNS tumours, 34 were diagnosed with AVP-D, including 4 with AAVP-D. Of these, 2 (50%) were male. In most cases, AAVP-D was identified shortly after the CNS tumour diagnosis, except for one patient who developed symptoms 9 years later. Case 1: A girl diagnosed with a germinoma at 3 years, treated with multiple surgeries and chemotherapy, presented at age 12 with somnolence, hypernatremia (serum sodium: 157 mmol/l, osmolarity: 311.3 mOsm/kg), and concurrent panhypopituitarism. Given the potential influence of adrenal insufficiency on ADH secretion, she was hospitalized for initiation and titration of desmopressin therapy, followed by hydrocortisone. Case 2: A 13-year-old female with a hypothalamic germ cell tumour treated with radiotherapy developed adipsia, anorexia, and hypernatremia (serum sodium: 159 mmol/l, osmolarity: 325 mOsm/kg). Panhypopituitarism was diagnosed, requiring desmopressin, hydrocortisone, and levothyroxine. Due to persistent inadequate hydration, nasogastric tube feeding was attempted but ineffective, necessitating chlorpromazine therapy, which successfully improved hydration and thirst perception. Case 3: An 18-year-old male with a germinoma developed panhypopituitarism and AAVP-D following CNS radiotherapy but achieved good sodium control after initiating desmopressin. Case 4: An 6-year-old male presenting with vomiting, severe headache, and hydrocephalus due to intraventricular haemorrhage developed polyuria and hypernatremia (serum sodium: 155 mmol/l). Initial management was difficult due to high sodium from low water intake. Increasing desmopressin and setting a fixed water intake plan with school teacher support improved symptoms.

Conclusion: AAVP-D is a rare form of arginine vasopressin deficiency, in which the lack of polydipsia poses a challenge for both diagnosis and management. Effective treatment requires a personalized approach, with acute management involving fixed doses of ADH analogues and carefully controlled water intake. For patients with concurrent endocrine deficiencies, hormone replacement is essential. In refractory cases, chlorpromazine may be considered to enhance thirst perception, offering a potential adjunctive therapy.