Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) and Subsequent Central Diabetes Insipidus: A Rare Presentation of Pituitary Apoplexy

Abstract

Pituitary apoplexy (PA) is a rare endocrine emergency that occasionally presents with sodium disturbances. Here we present a rare case with a previously healthy 41-year-old female who presented with acute onset headache and nausea without visual impairment or overt pituitary dysfunction. Plasma sodium concentrations declined abruptly during the first two days of admission to a nadir of 111 mmol/l. Urine and blood chemistry were consistent with syndrome of inappropriate antidiuretic hormone secretion (SIADH). Magnetic resonance imaging revealed recent bleeding into a pituitary cystic process. Hyponatremia was successfully corrected with fluid restriction and both visual function and anterior pituitary function remained intact. Subsequently, the patient developed central diabetes insipidus (CDI), which responded well to desmopressin substitution. To our knowledge, this is the first case of PA presenting predominantly with posterior pituitary dysfunction that transitioned from SIADH to permanent CDI.

Figure 1

Plasma concentrations of sodium. Horizontal axis depicts time course from hospital admission (day 0) until 180 days' follow-up. Vertical axis depicts plasma sodium concentrations (p-Na⁺). Hyponatremia was treated with intravenous hyperosmolar sodium infusion (3% NaCl at day 2) and fluid restriction (day 2 to day 5). The subsequent development of central diabetes insipidus (CDI) was treated with low dose desmopressin (initiated around day 60).

Figure 2

Magnetic resonance imaging of cerebrum. Magnetic resonance imaging (MRI) showed signs of recent bleeding into a cystic adenoma comprising 10x10x8 mm placed in sella turcica with close proximity to the chiasma and displacing the pituitary gland to the right.