Pituitary gland metastasis of breast cancer presenting as diabetes insipidus: A case report

Metastasis to pituitary gland is a rare condition, and patients are usually asymptomatic. Diabetes insipidus (DI) is the most common presenting symptom, and breast cancer is the most common source of pituitary metastasis (PM). We report a case of PM of breast cancer presenting as DI. A 45-year-old female patient presented to our department with complaints of polyuria and polydipsia. She had a medical history of metastatic breast adenocarcinoma. Laboratory data showed normal fasting plasma glucose level and hypotonic urine. Brain magnetic resonance imaging (MRI) showed infiltration of the pituitary stalk and the absence of the posterior pituitary bright spot consistent with metastasis to the pituitary gland. The water deprivation and vasopressin challenge tests confirmed central DI. Pituitary function tests revealed disconnection hyperprolactinemia with a menopausal profile. The patient was treated with vasopressin with great clinical results. Pituitary metastases are rare but should be suspected in patients with metastatic cancer who present with DI.