ODP292 A Xanthomatous Hypophysitis: Always Think Twice Before Pituitary Resection.
Authors: Panamonta Vipawee , Singhsnaeh Arunee , Korpaisarn Sira 
Published: November 2022

Abstract

Background
A xanthomatous hypophysitis is a rare form of primary hypophysitis common in females. Clinical case: A 47-year-old male was referred for pituitary adenoma resection. The patient presented with low libido and facial and body hair loss for 3 years. He reported increased thirst and nocturia for 2 years. 24-hr fluid intake showed 4,800 ml intake and 6,700 ml output. Physical examination revealed tanner 5 pubic hair with testicle size 12 ml bilaterally. He had a normal visual field. Laboratory testing revealed low morning total testosterone level of 108 ng/dL (241-872), low LH 0.39 mIU/mL (1.14-8.75) and low FSH 1.28 mIU/mL (1.37-13.58). Other pituitary hormones showed normal TSH 0.634 uIU/ml (0.35-4.9) with low free T4 0.64 (0.7-1.48), IGF-1 107 ng/mL (74-196), prolactin 10.92 mcg/mL (3.46-19.4), morning cortisol 8.9 mcg/dL (3.7-19.4). A 1 mcg ACTH stimulation test showed an inappropriate increase in cortisol level of 16.1 mcg/dL with baseline ACTH 28 pg/mL (0-46). Regarding polyuria, biochemical testing showed serum Na 148 mmol/L (136-145), Uosm 307 mOsm/Kg (50-1300), and Sosm 307 mOsm/kg (275-290). After the therapeutic trial with oral DDAVP, urine output significantly decreased. Subsequent tests showed serum Na 144 mmol/L, Uosm of 295 mOsm/kg, and Sosm of 278 mOsm/kg. The final diagnosis was hypopituitarism and central diabetes insipidus. MRI showed an enlarged pituitary gland with 2 decreased enhancing nodules in the post-contrast study of the anterior lobe measuring 4.2 and 6.7 mm in diameter. No stalk thickening was detected. There was no compression on adjacent organs. Since the pituitary lesions could not explain the hypopituitarism and DI. The surgery was postponed, and he underwent an endoscopic transsphenoidal biopsy. The procedure yielded a milky fluid content, and a circumferential dissection of a soft-yellow capsule was done. Pathology examination revealed a chronic hypophysitis with clusters of foamy macrophages. Immunohistochemistry showed positive for CD3, CD20, and CD138. A CD68 was positive in multiple clusters of foamy macrophages, while an IgG4 was negative. The final diagnosis is xanthomatous hypophysitis. The patient was treated with hormonal replacement therapy of levothyroxine, prednisolone, testosterone, and DDAVP. Until now, there are 36 cases in the literature reporting xanthomatous hypophysitis. The prevalences of hormonal deficits are 36.1% adrenal insufficiency, 42.4% central hypothyroidism, 54.6% central DI, 36.4% hypogonadism, 63.6% GH deficiency, and 54.6% hyperprolactinemia. The common MRI characteristic is a cystic mass with a ring or peripheral enhancement. Pituitary stalk thickening is shown in 50% of cases.

Conclusion
This clinical case demonstrated the rare entity of xanthomatous hypophysitis presenting with secondary AI, hypogonadotropic hypogonadism, central hypothyroidism, and DI. The discrepancy between clinical history and the MRI findings was a clue for pituitary biopsy leading to the final diagnosis and avoidance of unnecessary surgery.
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