7229 A Rare Case of Igg4 Hypophysitis Presenting as Hypogonadotropic Hypogonadism

Abstract Disclosure: C. Dimech: None. G. Jaiswal: None. Hypophysitis is a rare pituitary disorder including a broad range of inflammatory processes which affect the pituitary gland and infundibulum. Previously reported as 1 per 9 million individuals, the true incidence of hypophysitis per year is largely unknown due to the increase of novel etiologies such as immunoglobulin G4 (IgG4)- related disease. IgG4-related hypophysitis (IgG4-RH) was first clinically described in 2004 and later biopsy proven in 2007. The main clinical features are elevated serum IgG4 level and IgG4-positive lymphocyte infiltration of tissues on histopathology. IgG4-RH is reported to account for 1.3% of primary hypophysitis with 3.2:1 incidence ratio of men to women, in the 6th decade of life. Here we present a case of a 68-year-old Caucasian male who presented for evaluation of hypogonadotropic hypogonadism. As fasting morning testosterone levels were significantly low, MRI pituitary was completed which revealed a homogenously enhancing pituitary gland with thickened, nodular enhancement of the pituitary infundibulum. Subsequent lab work-up revealed normal function of remaining anterior pituitary without evidence of central vasopressin deficiency. Evaluation of underlying etiologies was unremarkable except for significantly elevated IgG4 levels (472mg/dL). Based on the significantly elevated IgG-4 levels (>135 mg/dl) and the radiographic findings of the pituitary infundibulum, the diagnosis of possible IgG4-RH was made. The patient was initiated on treatment with rituximab and glucocorticoid therapy with prednisone. Following 3 months of medical therapy, MRI pituitary showed resolution of stalk inflammation, confirming diagnosis of IgG4- RH. Presentation: 6/1/2024