Diabetes insipidus and adrenal insufficiency in a patient with metastatic breast cancer.

A patient previously treated for bilateral breast cancer with mastectomy, radiation therapy and in remission on hormonal therapy for more than five years presented with abdominal symptoms from breast cancer relapse. She developed inappropriate polyuria and hypernatraemia, which responded to desmopressin. In combination with the absence of a high signal from the posterior lobe of the pituitary on MRI , these data indicated the presence of partial central diabetes insipidus. The anterior pituitary showed partial failure (low follicle-stimulating hormone, luteinising hormone and insulin-like growth factor-1 levels). Furthermore, primary adrenal insufficiency had developed, ascribed to bilateral tumour invasion of the adrenals. This rare combination of endocrinological failures in a patient with metastatic breast cancer is discussed.