Unexpected Cause of Concurrent Hyponatremia and Hypokalaemia: A Case Report of Pituitary Adenoma

Rationale:In clinical practice, concurrent hyponatremia and hypokalaemia are commonly observed in the presence of thiazide diuretic use, gastrointestinal problems, or polydipsia.However, these conditions may mask rare causes, such as adrenal insufficiency, and lead to a delay in diagnosis.Patient concerns: Herein, we present a 71-year-old female with hypertension and type 2 diabetes mellitus, who presented to our emergency department with nausea and vomiting for the past several days.Hyponatremia and hypokalaemia were noted upon admission.Diagnosis: Initial impressions were consistent with Syndrome of Inappropriate Antidiuretic Hormone (SIADH) with water diuresis.However, even after water restriction, hyponatremia and hypokalaemia both persisted.Therefore, a pituitary lesion was strongly suspected.Further biochemical profiling of the pituitary hormones showed low Adrenocorticotropic Hormone (ACTH) levels.Interventions: Brain magnetic resonance imaging revealed a pituitary macroadenoma, which confirmed the diagnosis of secondary adrenal insufficiency due to ACTH deficiency.Outcomes: She was referred to the neurosurgery department for transsphenoidal removal of the pituitary adenoma.Lessons: This case suggests that clinicians should consider a diagnosis of secondary adrenal insufficiency when presented with a patient showing concurrent hyponatremia and hypokalaemia without an obvious aetiology.