SAT-236 Unusual Presentation of a Stable Pituitary Macroadenoma with Pituitary Apoplexy Causing SIADH and Pan-hypopituitarism

We are reporting a case of SIADH hyponatremia and pan-hypopituitarism in an otherwise stable appearing non-functional pituitary macroadenoma on MRI that suddenly developed apoplexy. Patient is a 52-year-old hispanic male with a history of a pituitary adenoma diagnosed initially on 06/2017 during MRI head for chronic headaches. MRI Pituitary on 07/2018 showed “well-circumscribed lesion” measuring approximately 12.7 x 14.8 x 13.4 mm in AP. Hormonal work up was normal in 06/2017, 01/2018, and 07/2018. In 07/2018 labs showed: IGF-1 247 ng/mL (65–222), ACTH 28 pg/mL (7–69), random cortisol 8.58 microg/dL (3.09–22.4), TSH 2.3 mIU/mL (0.4–5.5), fT4 1.06 ng/dL (0.8–1.8), LH 4.6 mIU/mL (0.98–79.7), FSH 6.2 MIU/mL (1–18), prolactin 2.92 ng/mL (2.1–24), and testosterone 310 ng/dL (87–814). Oral glucose tolerance test was done and showed: GH was 0.34 ng/mL at baseline and 1.01 ng/mL after 75 g oral glucose (equivocal result). Repeat IgF1 was normal after that. Subsequently, patient was admitted on 09/24/2018 with severe headaches, nausea, vomiting, polyuria, and polydipsia. He was hypotensive and tachycardic and was found to be hyponatremic with a Na of 124, lowest at 119 where hypertonic saline was given at that point. Urine output was 1.5 L in 24 hours while he was on an 0.8 L fluid restriction, and then 6 L the following day while he was on 1.5 L fluid restriction, serum osmolality was 251, urine osmolality was 1003, urine specific gravity was >1.030. Nephrology agreed to the diagnosis of SIADH. Blood work on 09/24 showed: random cortisol 0.67 microg/dL, TSH 0.19 mIU/mL, free T4: 0.63 ng/dL, ACTH 11 pg/mL, LH 2.4 mIU/mL, FSH 4.7 MIU/mL, testosterone 13 ng/dl. Patient was started on Levothyroxine 125 mcg and hydrocortisone stress dose. MRI brain was done and showed a pituitary macro-adenoma, measuring approximately 14 x 11 x 11 mm with no significant change in size since 6/30/2017, without optic nerve compression, no hemorrhage was mentioned. Work up for other causes of panhypopituitarism, i.e. hemochromatosis was done and was negative: Ferritin: 258 ng/mL (22–322). CT abdomen and pelvis was also done and showed normal adrenal glands. We thought about granulomatous infiltrative diseases like sarcoidosis since 1–25 (OH) vitamin D was high at 120 pg/mL (19.9–79.3). CT neck and chest was done but was negative for sarcoidosis or lymphadenopathy. Patient was seen outpatient by neurosurgery in 1/2019 and a repeat MRI was done which reported resolution of cystic and blood material from a pituitary adenoma, and per neurosurgery there is resolution of a pituitary cystic adenoma with apoplexy that now looks like a partial empty sella. Patient currently continues to be pan-hypopituitary requiring hydrocortisone, levothyroxine and testosterone replacement. SIADH has resolved. An otherwise non-functioning stable pituitary macroadenoma on MRI, can suddenly present as symptomatic apoplexy with SIADH and pan-hypopituitarism.