A woman with a history of triple-negative breast cancer developed central diabetes insipidus, a condition associated with metastatic involvement of the pituitary gland. Described in a case report by Francis T. Mutamba, a physician specialising in internal medicine, University Hospitals Birmingham NHS Foundation Trust, and colleagues, the complication stems from arginine vasopressin deficiency following cerebral metastases.
In Plain English: The Clinical Takeaway
- What happened: The patient experienced intense thirst, waking up twelve times a night to pass large volumes of water-like urine, alongside severe headaches and persistent dizziness.
- The underlying mechanism: A 9 mm lesion in the pituitary infundibulum disrupted hormone regulation, leading to a deficiency in arginine vasopressin.
- The treatment trajectory: Oral and intranasal desmopressin helped manage the excessive urination, while whole-brain radiotherapy targeted the advancing cerebral and pituitary lesions.
Pituitary Infiltration and Arginine Vasopressin Deficiency
The patient presented to clinicians with a five-week history of recurrent vomiting, dizziness, and worsening blurred vision, accompanied by severe, continuous headaches. Her primary complaints centered on profound fluid imbalance—specifically insatiable thirst, polyuria, and nocturia. Despite consuming large volumes of liquid, she produced large amounts of dilute, water-like urine that severely disrupted her sleep patterns and daily functioning.
Initial diagnostic workups revealed a hyperosmolar serum alongside low urine osmolality and low urine sodium, pointing to central diabetes insipidus. A brain MRI uncovered multiple cerebral metastases alongside a 9 mm lesion involving the pituitary infundibulum. This finding explained the arginine vasopressin deficiency.
Further hormonal assessments demonstrated secondary hypothyroidism and hypogonadotropic hypogonadism. These findings confirmed hypopituitarism secondary to metastatic infiltration of the gland.
Therapeutic Intervention and Rapid Disease Progression
Initial medical management involved oral levothyroxine at 50 µg daily and oral dexamethasone at 4 mg twice daily, paired with strict monitoring of fluid output. Clinicians established a threshold: if urine output exceeded 40 mL/kg/h, desmopressin treatment would begin. Subsequent endocrine reassessment showed urine output surpassing 4 liters per day, prompting the administration of 100 µg of oral desmopressin twice daily. Within 48 hours, her polyuria showed noticeable improvement.
However, persistent vomiting prevented the patient from tolerating oral medications. Medical teams shifted her regimen to intranasal desmopressin at 10 µg per dose twice daily, while intravenous dexamethasone replaced the oral formulation at 3.3 mg twice daily. A follow-up brain MRI revealed rapid advancement of the pituitary stalk and suprasellar mass, which expanded to measure 16 × 20.5 mm with newly formed cystic changes. Hospital staff referred her to the pituitary multidisciplinary team, where she underwent whole-brain radiotherapy during her admission.
| Clinical Parameter | Initial Presentation | Intervention / Adjustment |
|---|---|---|
| Primary Symptoms | Polyuria, polydipsia, nocturia, severe headaches | Urine output monitoring, fluid tracking |
| Hormonal Deficiencies | Arginine vasopressin deficiency, secondary hypothyroidism | Oral levothyroxine 50 µg daily, oral desmopressin |
| Imaging Findings | 9 mm pituitary infundibulum lesion, cerebral metastases | Rapid progression to 16 × 20.5 mm mass; whole-brain radiotherapy |
Multidisciplinary Management of Advanced Metastatic Complications
Despite targeted radiotherapy, the patient’s clinical status continued to deteriorate. Progressive frailty necessitated the involvement of a palliative care team. The authors of the case report stressed that clinicians should keep central diabetes insipidus in mind for metastatic breast cancer patients exhibiting electrolyte imbalances, polyuria, and polydipsia, particularly when these signs point to posterior pituitary involvement or outweigh the known extent of the disease.
The case underscores the necessity of early multidisciplinary management involving endocrinology, oncology, radiology, and palliative care when pituitary metastases occur in the setting of advanced malignancy. Operated by the National Library of Medicine at the U.S. National Institutes of Health, PubMed Central (PMC) functions as a complimentary archive providing full-text access to literature in the life sciences and biomedical journals.
Contraindications & When to Consult a Doctor
Patients diagnosed with advanced malignancies who experience sudden, uncharacteristic shifts in fluid balance—such as passing massive volumes of dilute urine alongside unquenchable thirst—require endocrine evaluation. Medical supervision is mandatory to prevent electrolyte disturbances.
References
- Mutamba, F. T., et al. A case report of a rare complication of breast cancer. University Hospitals Birmingham NHS Foundation Trust.
- National Center for Biotechnology Information (NCBI). PubMed Central (PMC) Full-Text Archive and Database Search Tools. PMC.
