6530 A Case of Lymphocytic Hypophysitis Followed by Acromegaly

Abstract Disclosure: L. Medina Mora: None. S. Htoo: None. A. Sanchez Ruiz: None. M. Harshan: None. M. Liu: None. Introduction: Acromegaly, a disorder with an estimated incidence of 0.28-0.4 cases per 100,000 individuals, is characterized by overproduction of growth hormone. Features include acral enlargement, frontal bossing, macrognathia, headaches, and hyperhidrosis. Comorbidities include hypertension, sleep apnea, type 2 diabetes, and cardiomyopathies. Hypophysitis, with an incidence of 1 in 9 million individuals, is an even rarer condition that involves pituitary gland inflammation. It can often lead to hormonal dysfunction and compression of surrounding structures. It is extremely rare for both acromegaly and hypophysitis to occur in the same individual. In this case report, we present a patient who developed lymphocytic hypophysitis followed by acromegaly. Case Report: A 58-year-old woman with a history of hypertension and lymphocytic hypophysitis (discovered during a workup of headaches without hormone derangement) returned to the clinic two years after complaining of progressive enlargement of her hands and feet, fragmented sleep, insomnia, and coarsening of facial features. She was found to have elevated IGF-1 (886 ng/mL; reference range: 48-235 ng/mL) and growth hormone levels (86.9 ng/mL; reference range: 0.12-9.88 ng/mL). An MRI showed a 2.9 x 3.2 x 3.8 cm suprasellar/sellar mass causing pressure on the optic chiasm, hypothalamus, third ventricle and midbrain. The patient underwent transsphenoidal resection (TSR), which was incomplete because the tumor was located behind the pituitary gland, followed by a right craniotomy to remove the remaining tumor. The tumor specimen stained positive for GH and PIT 1, exhibiting elevated proliferative indices (>2 mitotic figures per 10HPF, Ki-67 20%) and p53 labeling (5%). After the surgery, the patient's IGF-1 and GH levels normalized. However, her postoperative course was complicated by third cranial nerve palsy, diabetes insipidus, hypothyroidism, and secondary adrenal insufficiency. Discussion: Although TSR is the first-line treatment for most patients with acromegaly, it may not always result in a complete cure, as almost 50% of patients with macroadenomas do not achieve full surgical recovery. For persistent disease, medical therapy or transcranial surgery may be required. The tumor in this case was atypically proliferative, which was likely why GH and IGF-1 levels rose rapidly, manifesting in acromegalic symptoms in our patient two years after diagnosis of lymphocytic hypophysitis. The natural history of hypophysitis typically progresses from inflammation to fibrosis and subsequently to atrophy of the pituitary cells. This atrophy may cause changes in regulatory hormones that promote tumorigenesis. Therefore, hypophysitis may stimulate adenoma formation leading to acromegaly. More research is needed to characterize the relationship between these two rare entities. Presentation: 6/2/2024