Endocrine Abstracts

Introduction: Hyponatremia is defined as a serum sodium level of <135 mEq/l and it is considered severe when the serum level is below 125 mEq/l. In patients with diabetes insipidus treated with desmopressin, it is usually secondary to desmopressin overmedication.

Case report: A 79-year-old man, with a past history of post traumatic central diabetes insipidus treated with desmopressin. The patient had multiple admissions to the hospital due to hyponatremia, that were always associated to overmedication. He went to the emergency room because of asthenia, lethargy, headache, dizziness, nausea, paresthesias, polyuria and polydipsia and denied treatment with higher doses of desmopressin. The baseline endocrine tests revealed severe hyponatremia and hypochloremia with normal levels of potassium, hypercholesterolemia and low normal gonadotropins, total and free testosterone, prolactin, GH and IGF1. The dynamic pituitary reserve test established the diagnosis of panhypopituitarism and the water deprivation test confirmed central diabetes insipidus diagnosis. The magnetic resonance imaging revealed a normal-appearing pituitary gland with no pituitary tumour. The patient was treated with hydrocortisone, levothyroxine and desmopressin, with clinical and laboratory improvement.

Discussion: Although in this case report the most likely etiology to the hyponatremia was desmopressin overmedication, it caused multiple hospital admissions, persisted even after desmopressin dose adjustment and the laboratory tests of those admissions were not suggestive of overmedication. This suggests that other factor might be the cause or at least contributed to this ion change. Besides, the patient presented symptoms compatible with adrenal failure and hypothyroidism and had a head injury history, so other pituitary gland series deficiency might have developed over time. Therefore, panhypopituitarism and other hyponatremia causes must always be excluded in patients with diabetes insipidus, whose hyponatremia persists and is unresponsive to desmopressin dose adjustment.