Endocrine Abstracts

Introduction: Central diabetes insipidus is a disorder characterized by polyuria and polydipsia due to vasopressin deficiency caused by a lesion at the hypothalamo-hypophyseal axis. Frequently, central diabetes insipidus is wrongly considered idiopathic if not associated with other neurological signs and symptoms. Herein we present the report of a case that illustrates the difficulties in the diagnosis of this condition.

Case report: A 17 year-old male was admitted to our hospital with history of polydipsia, polyuria, and nocturia for 2 months with no neurological symptoms. These clinical manifestations characterized the presence of diabetes insipidus, so performance of a water deprivation test was indicated: after a 4-hour fasting period, there was increase in the plasma concentration with no increase in urinary concentration; 1 hour after the stimulus with desmopressin, there was an evident increase in urinary osmolality. Thus, we confirmed the presence of central diabetes insipidus, and therapy with desmopressin was initiated. We completed the study with a magnetic resonance that showed ‘Pituitary stalk with nodularity in its most cranial portion and iso-intense with respect to the adjacent parenchyma’. Considering the radiological and clinical findings and the absence of abnormality in the pituitary hormonal study, initial diagnosis was idiopathic central diabetes insipidus, nevertheless a close follow up of pituitary nodularity described would be done. Two months later, our patient referred frontal headache associated with nausea and vomiting, so a new magnetic resonance was performed. Imaging showed ‘a mass in the pineal region (18×18×19 mm) causing obstruction of the aqueduct of Silvio, with acute obstructive hydrocephalus data’. The most probable diagnostic hypothesis was pineal tumor; among these tumors, germinoma is the most common histological type and it was confirmed with a biopsy. Serum levels of alpha-fetoprotein and HCG were measured, with high level results for HCG. Radiotherapy was indicated, and it was performed with an initial satisfactory clinical and imaging response. However, our patient currently is receiving chemotherapy because of leptomeningeal tumor dissemination.

Conclusions: Our case report shows the difficulties in the diagnosis of tumors at the pineal region. Germinomas may have central diabetes insipidus as their first manifestation. The symptoms of diabetes insipidus may precede the alterations in the magnetic resonance. Whenever diabetes insipidus is present, we should perform a complete study, considering that the presence of these tumors cannot be discarded, even in cases of an initially normal neurological examination.