Polyuria, Polydipsia, and a Pituitary Mass: Uncovering Central Diabetes Insipidus

Introduction: Central diabetes insipidus (CDI) is a rare manifestation of pituitary masses. CDI results from a deficiency of antidiuretic hormone (ADH) release from the posterior pituitary gland, thus impairing renal water conservation and excessive free water loss. This abstract details a rare case of CDI in a female patient with a large pituitary macroadenoma, diagnosed prior to tumor resection. Case Description: A 66-year-old female patient with a medical history of Type 2 Diabetes Mellitus and Hypertension was transferred to our institution for neurosurgical evaluation of a pituitary mass. The patient stated that 10 days prior, she had developed a sudden headache, accompanied by vomiting, along with symptoms of polyuria and polydipsia. Brain magnetic resonance imaging showed a 1.6 cm-sized sellar mass associated with a small amount of surrounding intraparenchymal hemorrhage, consistent with pituitary apoplexy. She had no neurological defects. Laboratory workup showed preserved renal function, hypokalemia (2.9 mmol/L), metabolic alkalosis (36.9 mmol/L), hypernatremia (150 mmol/L), elevated serum osmolality (300 mOsm/Kg), and low urine osmolality (146 mOsm/Kg). Endocrine workup demonstrated evidence of hormonal hypersecretion consistent with Cushing’s disease. Urinary output exceeded 3L/day, confirming polyuria. A water deprivation test was performed and revealed consistent production of large volumes of dilute urine, confirming the diagnosis of CDI. Conservative management with desmopressin improved her serum sodium and symptoms. The patient was later managed with pituitary tumor resection without complications. Discussion: This case highlights the importance of recognizing CDI as a potential presenting symptom of pituitary macroadenoma, particularly in the context of pituitary apoplexy. Early identification and treatment with desmopressin are critical to correcting electrolyte imbalances and relieving symptoms. Although CDI is a rare manifestation of pituitary tumors, it may be the initial or only sign of underlying pathology. Prompt diagnosis and interdisciplinary management can significantly improve patient outcomes and guide appropriate surgical intervention.