Introduction: Central diabetes insipidus (CDI) is produced by the destruction of the magnocellular neurons of the hypothalamic supraoptic and paraventricular nuclei which results in decreased arginine vasopressin (AVP) synthesis and secretion.
Case report 1: Forty-five year old female, previously healthy, was observed in April 2011 complaining of polydipsia, polyuria, nocturia and weight loss since January. Diabetes mellitus (DM) was excluded and she was admitted for study of possible diabetes insipidus. Water deprivation test was suggestive of CDI. Magnetic resonance imaging (MRI) showed infundibular hypophysitis and no hyperintense signal in the neurohypophysis. Autoimmune diseases, infections and infiltrative diseases were excluded. Imaging (chest x-ray, abdominal ultrasound, mammography, breast ultrasound and thoracoabdominal CT) was normal. No other pituitary deficits were shown. She started therapy with oral desmopressin with clinical improvement.
Case report 2: Fourty-three year old man, previously healthy, was seen in August 2011 complaining of polydipsia, polyuria and nocturia during the previous 3 months. DM was excluded. Water deprivation test was positive for CDI. Pituitary MRI was normal, with normal signal of high intensity in the neutohypophysis. He had no other hormonal deficits. Autoimmune and infectous diseases were excluded. After initiation of oral desmopressin the symptoms disappeared.
Discussion: In both cases it was not determined the etiology of CDI, as it may occur in 2050% of CDI cases. In our institution is not possible to determine antibodies towards vasopressin secretory cells, which does not allow the diagnosis of this autoimmune form of CDI. The infundibular hypophysitis, observed in the first case, can occur in about 50% of idiopathic cases and more frequently in women. The lymphocytic hypophysitis can be diagnosed by pituitary biopsy, but its a very aggressive procedure and almost never performed. These cases highlight the difficulty of the etiologic diagnosis of CDI. However, proper treatment allows the symptoms control.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.