FRI342 Hypophysitis Mimicking As Pituitary Adenoma

Disclosure: A. Chao: None. A. Dhaliwal: None. K. Yu, MD: None. S.N. Polis: None. N.J. Vernetti: None. S. Nakhle: None. Background: Hypophysitis is defined as inflammation of the pituitary gland and causes include lymphocytic, granulomatous, xanthomatous, and IgG4 related hypophysitis. Hypophysitis can sometimes mimic a pituitary mass. It is more common in the female and associated with pregnancy. Lymphocytic hypophysitis may present with symptoms related to expansion of the pituitary gland and hormone deficiency. Expansion of the gland often causes headaches. Compression of the optic chiasm results in a decrease in the visual field, color perception, and in rare cases, diplopia due to lateral expansion of the pituitary gland.It also affects hypothalamic-pituitary axis and commonly impairs hormone production from corticotrophs, gonadotrophs and thyrotrophs. Patients treated with glucocorticoids can have hormonal recovery and resolutions of imaging findings. Clinical Case: Patient is a 30-year-old, previously healthy, female who initially presented to the emergency department with a worsening headache over the preceding three months. Brain MRI demonstrated a 1.8 cm enhancing mass and the radiologist interpreted the findings as a pituitary macroadenoma. The patient was seen by neurosurgery and was started on high doses of dexamethasone at 4 mg twice a day for three months duration. After treatment, the patient’s headache improved although she reported an 80-pound weight gain. CT of the head three months later reported a prominent pituitary gland in size compatible with history of pituitary adenoma but decreased in size to 0.9 cm. Repeated brain MRI six months after treatment showed resolution of the mass. The patient also noted a cessation of her menstrual cycle around the onset of headache and laboratory evaluation consistent with hypogonadotropic hypogonadism (FSH 5.5 mIU/mL, LH 2.8 mIU/mL and estradiol 22 pg/mL). Regular menstrual cycles returned seven months after glucocorticoid treatment. Almost two years after the onset of her headaches, the patient was referred to the endocrine clinic for further evaluation of fatigue, low libido, and persistent weight gain. Repeat anterior pituitary function tests were unremarkable and showed FSH 5.6 mIU/mL, LH 3.3 mIU/mL, Estradiol 34 pg/mL, Sodium 139 mmol/L, IGF-1 129 ng/mL (-0.4 standard deviation), Ferritin 20 ng/mL, Prolactin 15.6 ng/mL, TSH 4.38 mIU/L, T4 free 1.1 ng/dL, Cortisol AM 10.9 mcg/dL, and Testosterone 13 ng/dL. Conclusion: We present a case of hypophysitis mistaken for a non-functioning macroadenoma with mild mass effect on the undersurface of the optic chiasm, headache and hypogonadotropic hypogonadism. The patient did not have risk factors such as pregnancy or other autoimmune conditions. After glucocorticoid treatment, recovery of hypogonadotropic hypogonadism and resolution of headache, and radiographic findings. Presentation: Friday, June 16, 2023