7422 Adipsic Diabetes Insipidus Following Pituitary Macroadenoma Resection

Abstract Disclosure: J. Chippior: None. L. Ghalib: None. A 44 year-old female with a PMH of primary hypothyroidism, and a pituitary macroadenoma that was lost to follow up, presented to the ED with a chief complaint of an acute headache and decreased visual acuity involving the right eye over the past year. Patient was found to have a large, homogenous suprasellar mass with the largest dimension measuring 6.3 cm in size, and causing displacement of the optic chiasm. Initial hormonal workup was most notable for elevated prolactin at 128 ng/ml (3.3-26.7 ng/ml), which was slightly lower than when it was previously measured 10 years ago. The patient was taken to the OR for transsphenoidal endoscopic partial resection, but within 24 hours of post-op, she developed hypernatremia at 153 mmol/dL (135-145 mmol/dL) that was suspected to be secondary to diabetes insipidus (DI). In addition, she also suffered several small strokes involving her right midbrain and basal ganglia. She required multiple doses of DDAVP throughout her stay and this was ultimately continued upon discharge. Unfortunately, as follow up MRI had shown residual tumor within the third ventricle, she returned for a 2nd resection but once again suffered additional post-operative complications. The patient experienced additional strokes involving the right frontal and parietal lobes, and her DI became more labile than before, with her serum sodium peaking at 172 mmol/dL. Despite such a high degree of hypernatremia, she did not demonstrate any signs of thirst or any desire to access free water, even after her post-stroke encephalopathy had largely resolved. With less than 100 severe cases documented over the past four decades, it was suspected that the patient had a rare form of DI known as “adipsic DI”. Osmoreceptors within the hypothalamus can trigger the release of ADH or stimulate thirst, with the former requiring a smaller change in serum osmolality to generate such a response. Pituitary surgery involves manipulation of the infundibulum and any inadvertent severing can prevent ADH’s ability to travel from the hypothalamus to the posterior pituitary, subsequently leading to DI. The majority of patients with post-op DI increase their free water intake and subsequently do not develop hypernatremia. Those with adipsic DI lack this compensatory mechanism which leads to the electrolyte disturbance, and carries a higher risk of morbidity and mortality than those with typical DI. Following her second surgery, our patient was discharged with DDAVP once again but this time with a higher dose and frequency. She’s had numerous hospital readmissions since then for altered mental status in the setting of hypernatremia as she still struggles to meet her free water intake and continuously relies on her family for reminders. Though her case is certainly not typical, it highlights the added complexity of managing adipsic DI as it relies not only on DDAVP replacement, but replicating what is supposed to be an innate behavior. Presentation: 6/3/2024