Endocrine Abstracts

Arginine vasopressin deficiency (or central diabetes insipidus - CDI) is a rare disorder (1 in 25 000 individuals). It is characterised by decreased release of antidiuretic hormone (ADH) which results in polyuria and polydipsia. Majority of cases are acquired and caused by neurosurgery or head trauma, primary or secondary brain tumours, infiltrative diseases or autoimmune neurohypophysitis. Only about 5% of all reported cases are caused by genetic or congenital disorders. It has been suggested that an autoimmune process is involved in many patients with non-traumatic CDI (30-50%). Antibodies to AVP neurons were found in approximately one-third of the patients with ’idiopathic‘ CDI. We present a nineteen year old female, previously healthy, who presented in January 2022 with polyuria (10-12L daily), polydipsia (10-15L of water daily), nocturia (4-5 times) and nocturnal thirst during the previous 2-3 months. After excluding diabetes mellitus she was admitted to hospital to exclude possible diabetes insipidus. During the water deprivation test, laboratory tests showed low urine osmolality and mild plasma hyperosmolality. After administration of nasal desmopressin, urinary osmolality increased and the patient’s symptoms improved. Water deprivation test was positive for central diabetes insipidus. Magnetic resonance showed medially positioned infundibulum with thickened pituitary stalk (about 3.8 mm). There was no hyperintense signal (‘bright spot’) in the neurohypophysis. According to the radiologist, differential diagnosis of these changes could include lymphocytic hypophysitis. During hospitalization, extensive laboratory tests and imaging were done. Infiltrative diseases, infections including tuberculosis, and autoimmune diseases including sarcoidosis were excluded. Results of imaging (abdominal ultrasound, chest x-ray) were normal. There were no other pituitary deficits, or other hormonal deficits. The baseline hormone test showed slightly elevated prolactin level. Other laboratory tests showed high thyroid peroxidase antibodies. Ultrasound changes which indicate Hashimoto thyroiditis were found. After starting therapy with intranasal desmopressin, there was significant clinical improvement. Control MR imaging 9 months and 18 months after diagnosis showed no change in comparison with the first one. Desmopressin therapy was continued with excellent clinical and laboratory results.

Conclusion: The aetiologic diagnosis of central diabetes insipidus is difficult. The underlying cause remains unknown in many cases. This case did not show exact aetiology of central diabetes insipidus. We cannot determine vasopressin secretory cells antibodies, so possible autoimmune aetiology could not be confirmed. Although aetiology of the disease was not proved, proper treatment led to symptom control, clinical improvement and normalization of pathologic laboratory tests during 2 years after diagnosis.