Endocrine Abstracts (2011) 26 P646

Diabetes insipidus in a patient with breast carcinoma

J Couto, A P Santos, R Martins, L Giesteira & I Torres

Portuguese Institute of Endocrinology of Porto, Porto, Portugal.

Introduction: Central diabetes insipidus (CDI) is characterized by a deficient secretion of anti-diuretic hormone (ADH), in which a large volume of hypotonic urine is eliminated. Pituitary metastatic disease is rare, accounting for 1% of all excised pituitary tumors and generally involves the posterior pituitary. Neoplasms that more often originate pituitary metastases are breast and lung cancer. Breast cancer (BC) is associated with pituitary secondary involvement in 5.3 to 28% of cases.

Case report: The authors describe the case of a 50-year-old woman, previously diagnosed with breast cancer, who underwent surgery, chemotherapy, hormone therapy and radiotherapy. During follow-up she developed polydipsia, polyuria, and nocturia. The analytical study revealed serum osmolarity of 291 mosm/kg and urinary osmolarity of 182 mosm/kg. Biochemical and hormonal workup was normal. Pituitary MRI showed a nodular lesion, gadolinium emphasized, in the pituitary stalk, suggesting a metastatic lesion. Diffuse brain metastasis were also evident. The patient was treated with desmopressin, and there was clinical and analytical improvement. During follow-up liver and bone metastasis were diagnosed, her condition deteriorated and she died shortly after.

Conclusions: A case of CDI in the context of the pituitary stalk metastasis of BC is described. Owing to high etiologic clinical suspicion, water deprivation/vasopressin tests were not undertaken. Although symptoms resulting from metastatic lesions and pituitary adenomas are similar, CDI is described in only 1% of the latter and it has been suggested that its presence is the most important criterion in distinguishing between the two entities. In the context of malignancy, the emergence of CDI should alert the clinician to the possibility of pituitary’s metastatic involvement.

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