Endocrine Abstracts

Introduction: Central diabetes insipidus (CDI) in infants is rare and is often associated with intra-ventricular haemorrhage, congenital toxoplasmosis, intracranial tumours and anatomical abnormalities of the brain. We describe two cases of CDI associated with brain malformations, diagnosed at very young age with good response to oral DDAVP.

Case 1: A 34-week IUGR girl born to consanguineous parents (first cousins) developed hypernatraemia on day three of life. By day nine, inspite of an intake of 200 mls/kg/day serum sodium increased to159 mmol/L with urine output of 5–8 mls/kg/hr. She had lost 12.5% of birth weight. Paired serum and urine osmolality were 328 and 75 mOsm/kg respectively. A trial of intranasal DDAVP increased urine osmolality (306 mOsm/kg), decreased serum osmolality (297 mOsm/kg) and serum sodium (145 mmol/L) confirming CDI. Intranasal DDAVP was continued. Investigations revealed normal anterior pituitary functions. MRI brain showed absent rostrum and genu of corpus callosum, normal pituitary gland and optic nerves. Treatment is ongoing with oral DDAVP.

Case 2: A seven-week-old boy presented with one-day history of temperature, irritability and poor feeding. Clinical examination was unremarkable. Investigations revealed persistent hypernatraemia with sodium in the range of 151–160 mmol/L. Urine output was 4 mls/kg/hr. Urine and serum osmolality were 168 and 321 mOsm/kg respectively. Administration of intranasal DDAVP (200 ng) resulted in normalising of serum sodium (146 mmol/l) and urine osmolality (304 mOsm/kg) confirming the diagnosis of CDI. Anterior pituitary functions were normal. Ophthalmology examination confirmed bilateral marked optic nerve hypoplasia. MRI brain was consistent with septo-optic dysplasia. Treatment is ongoing with oral DDAVP.

Conclusion: CDI must always be considered as a differential diagnosis of unexplained persistent hypernatraemia. Intranasal DDAVP is useful in diagnosis while oral DDAVP is an effective treatment modality.