Severe Hyponatremia in a 46-Year-Old Female With Pituitary Stalk Duplication and Primary Empty Sella Syndrome.

Pituitary duplication is a rare congenital malformation. It has been mainly reported in the pediatric and neonatal population, with few reported cases in the adult population. In this case report, we discuss the presentation of an adult female patient with pituitary stalk duplication and primary empty sella (PES). A 46-year-old South Asian female presented with severe euvolemic hyponatremia. Initial investigation showed low serum osmolality, high urine osmolality, high urinary sodium concentration, and normal chest X-ray. On physical examination, the patient had underdeveloped secondary sexual characteristics. Laboratory tests showed low follicle-stimulating hormone, luteinizing hormone, and estradiol. Prolactin was moderately elevated, morning cortisol was low, adrenocorticotropic hormone (ACTH) was within the lower normal range, ACTH dynamic test was suboptimal, and insulin-like growth factor 1 was low. MRI showed empty sella with duplication of the pituitary stalk and third ventricle sagging. Pituitary stalk duplication is a rare congenital malformation that can be associated with other craniofacial abnormalities. Here, we describe the occurrence of pituitary stalk duplication with PES. It is not known if the two conditions are associated with each other. However, we speculate that the duplication of the stalk might have altered the normal anatomy of the aperture in the sellar diaphragm creating a space for the third ventricle to sag or herniate, as well as compressing the pituitary gland.