(CSEMP017) ISOLATED VASOPRESSIN DEFICIT ASSOCIATED WITH NIVOLUMAB: A CASE REPORT

Abstract:

Introduction: While immunotherapy is well known for causing various endocrine complications, isolated posterior pituitary dysfunction has rarely been reported.

Case description: We present the case of a 39-year-old female with metastatic gastric adenocarcinoma (lymph node, hepatic and ovarian metastases) admitted for malignant pericardial effusion. She was recently started on the Folfox protocol (folinic acid, fluoracil, oxaliplatin) and nivolumab every 2 weeks starting 7 weeks prior to this admission. Endocrinology was consulted for suspected vasopressin (AVP) deficiency. Following the first dose of immunotherapy, the patient noted a new onset of polydipsia and polyuria. In addition, she complained of nausea and vomiting a few days prior to admission. Calcium, glucose, and potassium levels were within normal ranges. HbA1c was 5.8%. Serum sodium level was 150 mmol/L and urine osmolality was 69 mmol/kg H2O. The urinary osmolality increased to a maximum value of 648 mmol/kg H2O six hours after administering 2 mcg of subcutaneous DDAVP, confirming the clinical diagnosis of AVP deficiency. Adrenal, thyroid and lactotroph axes were normal. The gonadotroph axis was considered indeterminate: the patient had a history of amenorrhea for several months prior to chemotherapy and immunotherapy, with undetectable estradiol levels and non-elevated nor suppressed FSH (7.1 UI/L) and LH (9.0 UI/L) levels. While somatotroph axis was not specifically evaluated, IGF-1 was normal. Magnetic resonance imaging revealed a slight thickening of the pituitary stalk with pituitary heterogeneity, suggesting hypophysitis. There were no pituitary lesions suspicious for metastasis. The posterior pituitary bright spot was absent. She was discharged with morning and bedtime oral DDAVP.

Discussion: Isolated posterior pituitary dysfunction associated with immunotherapy is a rare condition which needs to be differentiated from pituitary metastasis. Only five similar cases have been reported until now. This case highlights the importance of recognizing this rare condition despite the absence of anterior pituitary deficits. It also illustrates the variety of potential effects of immunotherapy on the endocrine system.