Endocrine Abstracts

Introduction: Hyponatremia, defined as a serum sodium concentration below 135 mEq/l, has a heterogeneous etiology, the main endocrine causes includind the syndrome of inappropiate antidiuresis (SIAD), adrenal insufficiency and severe hypothyroidism.

Materials and methods: Clinical, hormonal and imaging evaluation

Aim: To present a case of hyponatremia leading to the diagnosis of a large pituitary tumor

Case presentation: A 61 year-old male with a history of grandmal epilepsy treated with carbamazepine 600 mg/day, arterial hypertension, type 2 diabetes mellitus on oral antidiabetic drugs, obesity and dyslipidemia, presented initially to the ER for fatigue, nausea and emesis. Three weeks prior to presentation, he had undergone a laparoscopic intervention for an inguinal hernia. Physical examination revealed hypotension (BP=90/70 mmHg). Serum biochemistry revealed severe hyponatremia (107 mEq/l), hypochloremia and hypokalemia (2.5 mEq/l). Causes of pseudohyponatremia (hyperglycemia, hyperlipemia and hyperproteinemia) were ruled out. A cerebral CT scan demonstrated a pituitary tumor (2.1/2.7/3.1 cm) invading the right cavernous sinus. Biochemical tests of pituitary function demonstrated hypogonadotrophic hypogonadism and possible hypocortisolemia (5.8 μg/dl at 1300 h). Immediate administration of 3% NaCl and replacement of carbamazepine (a known SIAD cause) with levetiracetam led to gradual improvement. Ten days after initial presentation, the patient was admitted to our department for complete endocrine workup. On admission, clinical status was unremarkable, except for a right eye temporal visual field defect. Laboratory tests demonstrated panhypopituitarism and normoprolactinemia. His general status improved upon glucocorticoid replacement therapy followed by thyroid replacement. Ophtalmological examination showed optic chiasm syndrome, with right eye temporal hemianopia and left eye temporal and inferior quadrantanopia. The pituitary MDT recommended a pituitary MRI and neurosurgical evaluation, which are pending.

Conclusions: Our case illustrates the incidental discovery of a pituitary tumour and hypopituitarism in a pacient who already had a plausible cause of SIAD. Awareness of various causes of hyponatremia and attention to clinical detail are critical for detecting the complete etiology, which determines appropriate treatment in hyponatremia.