Diabetes insipidus in a patient with germinoma

Central diabetes insipidus (cDI) is characterized by a decreased release of antidiuretic hormone (ADH), resulting in a variable degree of polyuria. Besides lesions affecting the posterior pituitary, lack of appropriate ADH-secretion can be caused by disorders that act at one or more of the sites involved in the regulation of ADH secretion, e.g. the hypothalmic osmoreceptors, the supraoptic paraventricular nuclei or the superior portion of the supraoptical hypophyseal tract. In contrast to adult patients, where the vast majority of causes of cDI is post traumatic or following neurosurgical interventions, in children and adolescents tumors or infiltrative diseases are more common causes of central DI. Here, we report the case of a 17-year-old adolescent who developed polyuria due to a central nervous germinoma associated with diabetes insipidus. Water deprivation led to a persistent urine production with low osmolality as well as ADH plasma concentrations. Administration of vasopressin resulted in increased urine osmolality, thereby excluding nephrogenic DI. Magnetic resonance imaging (MRI) of the brain and spinal cord revealed a bifocal mass in the pineal region and suprasellar area surrounded by marginal oedema. Both, signalling sequences and localisation appeared typical for a germinoma. Furthermore, lumbar puncture revealed increased liquor concentrations of placental alkaline phosphatase and human chorionic gonadotropin, thereby providing further indirect evidence for a central germinoma. A combined test of the anterior pituitary demonstrated partial defects of the thyreo- gonado- and adrenocorticotropic function.

The patient was symptomatically replaced with desmopressin, 20mg of hydrocortisone, 50µg L-thyroxine and received a combined radio-/chemotherapy. The therapy was well tolerated so far and resulted in a radiological remission.