Prolonged hyponatremia due to hypopituitarism in a patient with non-ST-elevation myocardial infarction

A 58-year-old man was admitted for non-ST-elevation myocardial infarction. A medicated stent was used for severe coronary artery stenosis. However, consciousness level progressively deteriorated after angioplasty. Computed tomography showed no brain lesion but laboratory tests showed hyponatremia (serum sodium: 113 meq./l) and urine analysis showed syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH was first suspected to be drug-induced by enalapril. However, hyponatremia persisted even after withdrawal of enalapril and required oral sodium intake. Hormone assays indicated secondary adrenal insufficiency, which was caused by adrenocorticotropic hormone (ACTH) deficiency. Furthermore, in addition to ACTH deficiency, adult growth hormone deficiency was diagnosed following tests. Treatment with hydrocortisone relieved hyponatremia and re-institution of enalapril did not reduce serum sodium concentration. The final diagnosis was hyponatremia caused by hypopituitarism.