Endocrine Abstracts

Introduction: Hyponatremia is the most common hydroelectrolytic disturbance in clinical practice. Multiple causes exist for its occurrence, being the etiological diagnosis sometimes complex. In patients with suprasellar tumours it is even harder due to several confounding factors. Management of these patients is difficult as it conflicts with chemotherapy-associated hyperhydration protocols. We present a case that exemplifies this.

Clinical case: Four year-old female born in Angola diagnosed with a suprasellar pilomyxoid astrocytoma. She was submitted to a ventriculoperitoneal shunt and started chemotherapy with vinca alkaloids. Due to hypoosmolar hyponatremia, she was first diagnosed with secondary adrenal insufficiency and started therapy with hydrocortisone and, given the persistency, also fludrocortisone. When she was first seen in Endocrine department she was under 30 mg/day of hydrocortisone and 0.075 mg/day of fludrocortisone. She was clinically euvolemic and maintained hypoosmolar hyponatremia (sodium 130 mmol/l; osmolality 258.8 mOsm/kg) with low uric acid concentration and normal renal function. She presented with stage 2 pubic hair, probably due to iatrogenic pubarche. The pituitary axis evaluation was normal (ACTH 23.1 pg/ml; cortisol 15.2 µg/dl – without morning dose of hydrocortisone; TSH 0.75 µUI/ml; free T4 1.44 ng/dl; LH 1 mUI/ml; FSH 6.5 mUI/ml; estradiol 42 pg/ml). She started weaning off hydro and fludrocortisone and a syndrome of inappropriate antidiuretic hormone secretion (SIADH) due to brain tumor and/or vinca alkaloid therapy was suspected. She started hydric restriction and 0.25 g/kg of urea. Sodium levels were difficult to manage but documented as normal whenever the medication was strictly followed. She is now seven years old, Tanner stage 1, her tumor is stacionary in size (55 × 36 mm) under chemotherapy with a third line vinca alkaloide. She still needs medication to control hyponatremia.

Conclusion: The etiology of hyponatremia in this child was particularly challenging. Hyponatremia in this context is difficult to manage. We emphasize the potential complexity of correctly diagnosing and treating these patients.