Surgical Treatment Research Articles

7239 Natural history of cystic pituitary lesions

Abstract Disclosure: B. Graner: None. D.Z. Erickson: None. D. Donegan: None. Introduction: Pituitary lesions are a common incidental finding on brain MRI, the majority of which are cystic. The natural history and management of cystic pituitary lesions have not been clearly established. Purpose: The purpose of this study is to determine the natural history of incidentally identified cystic pituitary lesions, risk factors for growth and the proportion of patients who develop clinically significant symptoms requiring surgical intervention. Methods: Pituitary MRI reports between 01/01/2015 and 12/31/2022 in patients aged 18 years and older were searched for using Dig Our Radiology Information System (DORIS) using the words “cyst” or “cystic.” Additional inclusion criteria included a follow-up pituitary MRI of at least one year duration, clinical evaluation by Endocrinology, and the presence of a cystic pituitary lesion. Patients with non-contrast exams, excessive pituitary hormone secretion, and surgery within 1 year of presentation were excluded. Patient demographics, imaging characteristics of the lesion and clinical outcomes were collected. All pituitary MRI exams were reviewed by a single neuroradiologist. Results: A total of 157 MRIs in 56 patients with a mean age of 48 ±15 years were included, 39 (70%) were female. The mean follow-up was 2.3 ± 1.4 years. The most common indication for MRI was headache (n= 18, 32%). There was no significant difference in mean maximum (max) diameter at last follow-up compared to baseline (7.45 ±4.23 vs 7.04 ±4.35 mm, p=0.06) or mean cyst volume (197.08 ±252.68 vs 201.43 ±326.18 mm3). Nine (16%) of the lesions increased in volume with a mean change in volume of 105 ±133.64 mm3/yr, note 11 (20%) decreased volume and 36 (64%) remained the same size. Using univariate logistic regression, the odds of cyst growth was greater the larger the max diameter (p= 0.03) or volume was at baseline (p= 0.02)/ Female sex (p=0.32), age at diagnosis (p=0.70) or whether the lesion was thought to be a Rathke cleft cyst or a cystic adenoma (p=0.80) were not associated with increased odds of growth. The risk of growth was higher (42 vs 9%, p=0.016) and the volume change per year was greater (67.2 ±134 vs -7 ±28 mm3, p=0.04) in those with a baseline max diameter of >10 mm. Surgery was performed in 4 patients (7%), 3 of which demonstrated lesion growth (baseline size 12-15 mm and growth rates of 59-341mm3/yr). Pathology revealed one Rathke cleft cyst, one cystic adenoma and fibrotic pituitary changes. The fourth surgical patient opted for resection at an outside facility without a demonstrated increase in size (Rathke cleft cyst). Conclusion: The majority of incidentally found cystic pituitary lesions do not increase after an average follow-up 2-3 years. Growth necessitating surgical intervention was only required in 5% of patients over the study period. A pituitary cyst >10 mm at diagnosis was associated with an increased risk of growth and therefore warrants closer follow-up. Presentation: 6/1/2024

Oral and Pharyngeal Diverticula: A Rare Case of Dysphagia and Diagnostic Challenges

This report describes the case of a 62-year-old male patient in Saudi Arabia who developed a diverticular pouch in his oral cavity. Diverticula are rare conditions that appear as protrusions or pouches within the digestive tract’s inner lining. The condition can occur in different parts of the digestive system, but the colon is the most affected part. As part of the patient’s symptoms, he presented with dysphagia, weight loss, and globus sensations. Multiple diagnostic tests, including ultrasound, computerized tomography (CT), and magnetic resonance imaging (MRI), did not identify the diverticula. Barium and upper gastrointestinal studies were the diagnostic tests that provided accurate diagnoses where several diverticula were discovered during the videofluoroscopic swallow study (VFSS) and fiberoptic endoscopic evaluation of swallowing (FEES). Surgical intervention was recommended by the multidisciplinary team; however, the patient rejected this treatment option. This report highlights the necessity for instrumental swallowing diagnostic evaluation in the workup of the infrequent etiologies of dysphagia and suggests a gap in the current knowledge, prompting further studies on the etiology, incidence, and optimum management of upper gastrointestinal (GI) tract diverticular disease.

7536 Missed Silent Retroperitoneal Paraganglioma

Abstract Disclosure: S. Lamichhane: None. D.T. Price: None. J.J. Faria-Briceno: None. A. Kaur: None. Introduction: Paragangliomas are rare neuroendocrine tumors comprising about 15-20% of all chromaffin cell tumors and can arise anywhere along the sympathetic and parasympathetic ganglionic chain from skull base to the pelvic floor. About 75% of sympathetic paragangliomas arise in the abdomen out of which majority are functional and secrete catecholamines responsible for the typical clinical features. While the diagnosis is usually made by clinical features and lab elevation of catecholamines, it is estimated that 10-15% of paragangliomas are non-functional and another 10% do not manifest clinically according to the hormone activity, thus posing a significant diagnostic challenge. We report a case of a retroperitoneal paraganglioma diagnosed by biopsy as it was initially missed owing to its silent nature clinically and biochemically. Case report:A 48-year-old smoker with panic disorder, remote history of spontaneous pneumothorax, and exploratory laparotomy for motor vehicle accident visited ER due to left-sided abdominal fullness and weight loss of 10-20 pounds for several months. Review of systems was negative except for mild constipation. He denied taking any medications and BP had been normal. CT abdomen showed a large 13.3 cm mixed cystic and solid mesenteric mass. Core biopsy revealed pheochromocytoma and patient was referred to Endocrinology. Labs showed elevated plasma free metanephrines (MN) 80 pg/ml, normetanephrines (NMN) 190 pg/ml, total MN 270 pg/ml, all less than twice the upper limit of normal and inconclusive, non-elevated 24-hour urine MN and NMN but with inadequate collection, and normal plasma catecholamines. MRI revealed a 13.5 cm mass in the left retroperitoneal sympathetic chain separate from the left adrenal gland and inferior to the left kidney. After pre-op optimization with alpha and beta blocker, patient had an uncomplicated open resection of the mass along with the retroperitoneal lymph nodes (LN). Pathology resulted in 3 benign LNs, a 16.5 cm paraganglioma negative for margin, lymph-vascular invasion, and necrosis. Genetic panel was negative. Follow-up post-surgery at 1 and 3 months with mildly elevated catecholamines and MRI abdomen at 3 months without evidence of recurrent or residual mass and metastasis. PET scan is pending prior authorization. Conclusion: Silent retroperitoneal paragangliomas are exceedingly rare. The diagnosis is often missed when the tumors are asymptomatic, and biomarkers are not elevated. The lack of specific imaging characteristics also adds to the diagnostic challenge. Early recognition can avoid the potential risk of life-threatening hypertensive crisis during surgical intervention. Our case highlights the importance of considering this rare entity in the differential diagnosis of retroperitoneal mass. Presentation: 6/1/2024

8592 Parathyroid Carcinoma: A Rare Cause of Primary Hyperparathyroidism

Abstract Disclosure: S.E. Koshy: None. C.F. Mulcahy: None. P.S. Kothari: None. E.M. Jacobi: None. T.D. Cubb: None. Introduction: Parathyroid carcinoma (PC) is a rare malignancy that accounts for <1% of cases of primary hyperparathyroidism (PHPT). Patients often present with symptoms of hypercalcemia, serum calcium (Ca) >14 mg/dL, large tumor size, and a very high parathyroid hormone (PTH) level. We report a case of an asymptomatic patient with incidentally found hypercalcemia consistent with PHPT who was ultimately diagnosed with PC. Clinical Case: A 31yo male was found to have elevated serum Ca of 12.7 mg/dL (8.6-10.3 mg/dL) on labs obtained during routine physical exam. He had no known significant medical or family history and notably had no laboratory evaluation within the prior 10 years. He denied constipation, polyuria, confusion, depression, bone pain, and history of fractures or nephrolithiasis. Workup showed an inappropriately elevated PTH of 505 pg/mL (16-77 pg/mL). Neck ultrasound demonstrated a left inferior 3.9 cm complex thyroid nodule. Sestamibi scan confirmed increased uptake in the inferior left thyroid. Left neck exploration was performed. Intraoperatively, a 3.7 cm left parathyroid mass weighing 13.0 grams was encountered and excised in an en bloc fashion. The left superior parathyroid gland was evaluated and found to be normal. Intraoperative PTH level decreased from 529 pg/mL to 48 pg/mL 10 minutes after excision. Left hemithyroidectomy was not performed. Surgical pathology revealed PC with lymphovascular invasion, suspected capsular invasion, and negative margins. Immunohistochemical staining showed a Ki67 proliferation index up to 5% and complete loss of nuclear staining for parafibromin. Next generation sequencing demonstrated a somatic CDC73 p.L8fs mutation, tumor mutational burden 4.7m/MB, and stable microsatellite instability. Germline testing was negative for a CDC73 mutation. Postoperative staging did not demonstrate evidence of metastatic disease in the neck or chest. Serum Ca remained within normal limits. After multidisciplinary discussion, no further surgical intervention was recommended and plan was for ongoing biochemical and imaging surveillance. Conclusion: Though rare, PC should be considered as a cause of PHPT. The primary treatment is complete surgical resection. Unfortunately, there is a high rate of recurrence, >50%, with most occurring 2-5 years after initial surgery with a median overall survival of 14 years. Thus, long-term surveillance is of utmost importance. Treatment of recurrent disease is surgical resection when feasible as well as medical management of hypercalcemia. Further research is needed to better understand the role of targeted systemic therapy in addition to immunotherapy. PC is most commonly sporadic but can be hereditary, thus genetic evaluation is recommended. Given its rarity and complexity, PC is best managed in a multidisciplinary setting. Presentation: 6/1/2024

7246 Cardiac Paraganglioma: A Rare Entity

Abstract Disclosure: L. Javed: None. L. Jonea: None. Cardiac paragangliomas are an exceptionally uncommon subset of neuroendocrine neoplasms. We present a case of a patient presenting with this condition. 70-year-old woman with pertinent past medical history of chronic veinous insufficiency complicated by recurrent abscesses of her right leg since venaseal procedure. The patient had positive IgG lambda on immunofixation that raised concerns for MGUS. Therefore, a F-18 FDG PET-CT scan was performed for further evaluation. PET-CT revealed a hypermetabolic mass in the upper inner right thigh and the right atrium (SUV 17.6) raising concern for septic thrombi. She was admitted in the hospital for initiation of antibiotic therapy. Transesophageal echocardiogram (TEE) revealed a 4.5 cm x 4.0 cm mass in the right atrioventricular (AV) groove region, extending over the root of the main pulmonary artery. Following discharge, despite completing six weeks of IV antibiotic therapy a CT scan on a subsequent clinic visit revealed the same mass as seen on TEE. CT imaging raised suspicion of neuroendocrine tumor. This led to referral to the endocrinology department. Laboratory results showed elevated normetanephrine and dopamine levels increasing likelihood of paraganglioma. Lab Results: 24 hr urine normetaneprhine :7197(N ≤ 376 mcg), 24 hr urinary dopamine :879 (N ≤400 mcg), 24 urinary metanephrine: 84 (N ≤96 mcg) & 24 hr urinary epinephrine <3 (N ≤20 mcg). Her home systolic blood pressure readings varied between 120’s & 170’s. She was initiated on Prazosin 1 mg daily in addition to the existing antihypertensive medications of nebivilol, amlodipine & furosemide. Few months later, this patient successfully underwent cardiac mass resection. Histologic findings of the resected mass were consistent with paraganglioma. Post-surgery, anti-hypertensive medications were discontinued, and blood pressure normalized to systolic readings in the 90s to 120s and diastolic readings in the 60s to 80s. Repeat biochemical tests indicated a normalization of normetanephrine & dopamine levels, validating the success of the resection. This case features an extremely rare entity cardiac paraganglioma that had an atypical clinical manifestation of being asymptomatic. Timely diagnosis and appropriate management are crucial for patient outcomes. Surgical intervention, although fundamental, bears significant risks, necessitating meticulous preoperative management to mitigate potential complications. The medical approach focuses on averting perioperative complications such as hypertensive crisis, cardiac arrhythmias and myocardial infarction. This is achieved by administering alpha and beta adrenoceptor blockers for a minimum of two weeks before the scheduled surgery. Regular follow up is also essential due to the unpredictable malignant potential of these tumors. Presentation: 6/3/2024

7078 Diagnostic Obstacles in Thyroid-Stimulating Hormone-Secreting Pituitary Adenoma (TSH-oma): A Case Report

Abstract Disclosure: V.A. Mendpara: None. P.P. Rao: None. M.D. Lundholm: None. Background: Thyroid-stimulating hormone-secreting pituitary adenoma (TSH-oma) is a rare cause of hyperthyroidism, forming 0.5-3% of all functioning pituitary tumors and <1% of hyperthyroid cases. Here, TSH secretion is autonomous and unresponsive to the normal negative feedback of thyroid hormones, leading to inappropriate TSH, T4 and T3 elevation. In the absence of clinical symptoms it can be difficult to distinguish between thyroid hormone resistance (THR) and lab errors. Clinical Case: A 44-year-old Swahili-speaking female with a history of type 2 diabetes was admitted for hypoglycemia requiring insulin adjustment. In her workup, thyroid function tests were obtained, revealing normal or low TSH (0.28 mIU/L) and high free T4 levels (2.7 ng/dL). At outpatient follow-up, repeat labs showed elevated TSH, T3 and FT4 (5.22 mIU/L, 377 ng/dL and 4.7 ng/dL, respectively). She reported weight loss, occasional palpitations, and chronic insomnia but denied other symptoms. Graves' antibodies (TSI, TSHR Ab) were negative. On exam, she had a 30-40 gm, smooth, non-tender thyroid without adenopathy, and a BMI of 23 kg/m2. The initial differential diagnosis included TFT lab error, THR or TSH-oma. A FT4 by equilibrium dialysis was high at 7.8 ng/dL (1.1-2.4 ng/dL). N-telopeptide (NTX) and sex hormone-binding globulin (SHBG) were elevated, consistent with a true hyperthyroid state. Genetic testing for THR posed time and cost barriers. Elevated alpha-subunit levels (87 ng/mL, normal ≤1.8 ng/mL) with normal levels of other pituitary hormones prompted a pituitary MRI, unveiling a 4.7 cm suprasellar bilobed pituitary mass abutting the optic chiasm and invading the cavernous and sphenoidal sinuses. She denied peripheral vision loss or headaches. Hyperthyroidism was managed with methimazole until surgical intervention for the TSH-oma. A transsphenoidal resection was performed with histopathological confirmation of a TSH-staining pituitary adenoma. She was started on levothyroxine for central hypothyroidism thereafter. Discussion: It is challenging to find the cause of abnormal TFTs when patients are asymptomatic and the differential includes THR, lab errors or TSH-oma. Inaccurate diagnosis can lead to delays in care or unnecessary thyroid ablation or pituitary surgery. Conversely, early identification and appropriate treatment of TSH-omas can prevent neurological and endocrinological complications, such as optic chiasm compression, visual disturbances, headache and hypopituitarism. Despite a lack of convincing symptoms of hyperthyroidism, we used confirmatory labs (NTX, SHBG) to rule in biochemical hyperthyroidism along with alpha-subunit testing and pituitary MRI to solidify the TSH-oma diagnosis, leading to surgical intervention. This case highlights the vital steps in the diagnosis of a TSH-oma, emphasizing the need for logical evaluation and differentiation of this rare condition. Presentation: 6/1/2024

7202 CPP with Rapid Pubertal Progression in a 9-Year-Old Boy with Hypothalamic Teratoma

Abstract Disclosure: R. Robilliard: None. G. Tung: None. K. Svokos: None. R. Lulla: None. J.Q. Quintos: None. Background: Central Precocious Puberty (CPP) in males is rare, with incidence of 0.01-2/10,000. The most common identifiable cause of CPP in young children is hypothalamic hamartoma. No case hypothalamic teratoma has been reported to cause CPP in males. Clinical Case: At the age of 10-years and 5-months, a boy presented to the pediatric endocrinology with signs of precocious puberty including facial hair development, voice deepening, and increased growth velocity that began at 9 years old. There was no significant past medical history and he denied headache, blurry vision, or diplopia. Physical examination showed height of 140.4 cm (47%), Tanner 4 genitalia, Tanner 3 pubic hair, and testicular volumes of 15 cc (left) and 12-15cc (right). Bone age (BA) determined by radiography was 13.5 years with a predicted adult height (PAH) of 63 inches. The mid-parental target height was 67 +/- 4 inches. Evaluation including TSH, glucose, serum and CSF β-HCG, DHEA, CSF AFP was normal. Serum LH was 2.9 IU/L and testosterone level was 109 ng/dl, consistent with CPP. MRI of the pituitary showed a small, heterogeneous and fat-containing lesion extending inferiorly from the tuber cinereum consistent with teratoma. Treatment included GnRH agonist Lupron (30mg) every 3 months. Laboratory evaluation 8 months after initial presentation showed suppressed LH of 0.9 IU/L and FSH 0.5 mIU/mL, and testosterone of 57 ng/dL. Repeat radiography for BA one year after GnRHa suppression showed BA of 14 years at CA of 11 years 6 months and PAH of 64.4 inches. Growth velocity slowed to 5.3 cm/year. At the most recent follow-up visit at CA of 12 years, height was 151.5 cm (61%), growth velocity 6.3 cm/year (74% for age), Tanner 5 penis and pubic hair, left testicular volume of 15-20cc and right testicular volume of 15 cc. Most recent radiographic BA is14 years, and PAH is 65.9 inches. Given response to GnRH agonist injections every 3 months, the absence of CNS symptoms referable to the teratoma and no change in MR imaging, no surgical intervention is recommended. Conclusion: This is the first case of a hypothalamic teratoma reported in a male associated with CPP. Despite this rare cause, the patient has responded to standard treatment with GnRH agonist therapy alone. Presentation: 6/1/2024

9182 Metastatic Extra-Gastrointestinal Stromal Tumor Presenting As Hypoglycemia

Abstract Disclosure: O. faour: None. D. John: None. S.K. Suryanarayanan: None. A.A. Rizvi: None. Introduction: Non islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome seen in association with solid abdominal tumors of mesenchymal and epithelial origin. We report a case of metastatic extra-gastrointestinal stromal tumor (E-GIST) presenting with severe hypoglycemia as its initial manifestation. CASE DESCRIPTION: A 46-year-old patient was found to have a blood glucose of <45 mg/dl during a routine clinic visit with her primary care physician. Although she was asymptomatic, she was sent to the emergency room (ER) for further evaluation. She had a history of prediabetes managed by lifestyle modification. She has been experiencing multiple episodes of hypoglycemia previously which fulfilled the Whipple’s triad in the preceding months. These hypoglycemic episodes included loss of unconsciousness, falls in the shower with head injury, and several hospital visits. Serum glucose in the ER was 14 mg/dl and hypoglycemia persisted despite continuous dextrose solution. Physical examination was notable for a distended, non-tender abdomen and cervical lymphadenopathy. CT scan showed a 15 cm mass in the liver, multiple large masses in the mesentery, and a 11 cm lesion in the left pelvis. There were enlarged lymph nodes in the abdomen, chest, and neck. Serum chemistries drawn when the patient was hypoglycemic revealed potassium level of 2.7 mg/dl (3.5-5.5) an insulin level of <1.0 mIU/L (5-25), C-peptide <0.1 ng/mL (0.5-2), cortisol 13.8 mcg/dL (5-25), and insulin-like growth factor-2 (IGF-2) was 270 ng/mL (38-267). The IGF-2/IGF-1 molar ratio was 3.4 (normal <3:1). The sulfonylurea drug screen came back negative. Upper and lower endoscopies were unrevealing. Biopsy of the liver lesion showed cytology and immunohistochemical findings consistent with a epithelioid metastatic extra-gastrointestinal stromal tumor. A provisional diagnosis of NICTH was made. The patient responded well to intravenous glucose, oral carbohydrate intake and high-dose corticosteroids. She was subsequently started on therapy with the tyrosine kinase inhibitor (TKI) imatinib. Discussion: Paraneoplastic hypoglycemia is often seen in association with metastatic epithelial and mesenchymal tumors. IGF-2 and incompletely processed pro-IGF-2 activates autocrine, paracrine, and endocrine pathways that lead to tumor growth, fasting hypoglycemia, rarely of acromegalic features. Treatment with octreotide, diazoxide, and glucagon is generally ineffective, while glucocorticoid use and surgical intervention are helpful in ameliorating the hypoglycemia. Tumor-directed therapy with TKIs, primarily imatinib, appears promising in achieving remission. Our case is a clinical reminder that hypoglycemia secondary to NICTH can be the predominant presenting feature in patients with underlying E-GIST. Presentation: 6/3/2024

12350 A Rare Case Of Giant Parathyroid Adenoma Managed Medically For 8 Months: A Case Report

Abstract Disclosure: S. Labram: None. L. Bilandzic: None. Background: Single parathyroid adenoma is the most common cause of primary hyperparathyroidism, and is attributed to approximately 85% of cases[1]. However, those classified as giant (weighing over 3.5 g and having a size greater than 2cm2) are exceedingly rare. This reports a rare case of primary hyperparathyroidism caused by giant parathyroid adenoma and details biochemical response following medical and surgical management. Case Report: A 64 year old black female presented with severe abdominal pain, confusion and constipation. Investigations revealed severe hypercalcemia of 17.3 mg/dl with massively elevated parathyroid hormone of 1255 pg/mL. Ultrasound showed a large hypoechogenic lobulated mass inferior to the left thyroid lobe representing a giant parathyroid adenoma. Due to delayed surgery the patient was initially treated medically over the course of 8 months. Over these months she was admitted to hospital 3 times for symptomatic hypercalcemia and received a total of 3 zolendronic acid infusions. Despite this she was unable to achieve long term remission of hypercalcemia. Cinacalcet was added and tolerated at the dose of 30 mg daily. Hypercalcemia improved, but remained elevated at a range of 11-13 mg/dL and the symptoms of brain fog and constipation did not subside entirely. She was eventually able to undergo surgical resection, and a giant parathyroid adenoma weighing 8.9 g was excised. Intraoperative intact parathyroid hormone (IOiPTH) sampling showed > 50% reduction (prior to removal 878pg/mL, 10 minutes after removal 132 pg/ml, 20 minutes after removal 96pg/mL). Pathological review showed an atypical parathyroid tumor. As the tumor lacked invasive growth it did not meet criteria for carcinoma. Conclusions: This is a rare case of primary hyperparathyroidism caused by a giant solitary parathyroid adenoma. The gold standard for management of primary hyperparathyroidism secondary to parathyroid adenoma is minimally invasive parathyroidectomy. However in our case, due to inability to access immediate surgery, challenging and prolonged medical treatment of severe hypercalcemia followed for 8 months. Ultimately, normalization of calcium level was achieved only by surgical intervention. IOiPTH measurements showed appropriate decrease confirmatory for the complete removal of the adenoma.

6777 Exploring the comorbidity in males with 45,X/46,XY mosaicism unveils a pattern mirroring that of Turner syndrome

Abstract Disclosure: K. Stochholm: None. C.H. Gravholt: None. A. Berglund: None. Background: Males with 45,X/46,XY mosaicism are rare with an apparent prevalence of 6 per 100,000 newborn males. Knowledge about associated health outcomes are limited. Females with 45,X/46,XY fall under the Turner syndrome diagnosis but males do not. Aim: To investigate the comorbidity pattern in a national cohort of males with 45,X/46,XY. Methods: Morbidity were investigated using Cox regression analysis on administratively longitudinally collected registry data regarding hospital diagnoses, prescribed medication, and surgery codes. Data were retrieved for all males diagnosed with 45,X/46,XY from 1960 to 2018 (n=135) and for 13,500 age-matched males from the general population, who served as comparator. Results: 45,X/46,XY was associated an increased overall risk of receiving a hospital diagnosis (HR: 1.6, CI: 1.3-1.9), being prescribed medication (HR: 1.2, CI: 1.03-1.5), and undergoing a surgical procedure (HR: 1.8, CI: 1.4-2.1). Dividing hospital diagnoses into 18 chapters according to the International Classification of Diseases (ICD-10), 45,X/46,XY had a significantly increased risk of diagnoses in all but three chapters. Among diagnoses with a significantly increased risk were gonadal dysfunction (HR=63.7, CI: 34.8-116.9), short stature (HR=24.7, CI: 10.0-60.6), pubertal disorders (HR=25.8, CI:7.2-92.6), type 1 (HR=4.1, CI: 1.8-9.4) and type 2 diabetes mellitus (HR=3.4, CI: 1.7-6.6), thyroid disorders (HR=3.8, CI: 1.4-10.4), obesity (HR=4.4, CI: 2.3-8.2), osteoporosis and osteopenia (HR=5.4, CI: 2.4-12.3), hearing loss (HR=2.2, CI: 1.3-3.8), otitis media (HR=1.6, CI: 1.3-1.9), ischemic heart disease (HR=2.4, CI: 1.3-4.4), hypertension (HR=2.3, CI: 1.4-3.9), inflammatory bowel disease (HR=2.5, CI: 1.2-5.4), cryptorchidism (HR=11.9, CI: 7.8-17.8), hypospadias (25.9, CI: 14.0-47.8), testis cancer (HR=6.4, CI: 2.0-20.6), infertility (HR=23.5, CI: 16.0-34.4), gynecomastia (HR=4.6, CI: 1.7-12.5), horse shoe kidney (HR=177,8, CI: 16.1-1968.8), coarctation of the aortae (HR=66.0, CI: 11.0-394.9), and bicuspid aortic valve (HR=53.4, CI: 12.7-223.7). Conclusion: Males with 45,X/46,XY mosaicism exhibit heightened morbidity, evidenced by a notable surge in hospital diagnoses, prescribed medications, and surgical interventions. This increased morbidity is linked to a broad spectrum of diseases, showcasing a comorbidity pattern reminiscent of Turner syndrome. This study emphasizes the need for systematic follow-up in individuals with 45,X/46,XY mosaicism, highlighting the imperative for proactive healthcare management in this population. Presentation: 6/1/2024

An Uncommon Cause of Peritonitis: Perforation of Undiagnosed Gastric Cancer

Gastric cancer, while common, rarely presents as an acute surgical emergency, with perforation occurring in less than 5% of cases. This report details a 53-year-old male who presented with abdominal pain and vomiting, leading to a diagnosis of perforated gastric adenocarcinoma confirmed by imaging and subsequent total gastrectomy. The case underscores the challenges of diagnosing perforated gastric cancer, which often mimics benign conditions. Effective imaging, especially CT scans, is crucial for timely diagnosis and management. Given the high mortality associated with surgical interventions, further research is needed to establish standardized treatment guidelines for this rare complication.

8592 Parathyroid Carcinoma: A Rare Cause of Primary Hyperparathyroidism

Abstract Disclosure: S.E. Koshy: None. C.F. Mulcahy: None. P.S. Kothari: None. E.M. Jacobi: None. T.D. Cubb: None. Introduction: Parathyroid carcinoma (PC) is a rare malignancy that accounts for <1% of cases of primary hyperparathyroidism (PHPT). Patients often present with symptoms of hypercalcemia, serum calcium (Ca) >14 mg/dL, large tumor size, and a very high parathyroid hormone (PTH) level. We report a case of an asymptomatic patient with incidentally found hypercalcemia consistent with PHPT who was ultimately diagnosed with PC. Clinical Case: A 31yo male was found to have elevated serum Ca of 12.7 mg/dL (8.6-10.3 mg/dL) on labs obtained during routine physical exam. He had no known significant medical or family history and notably had no laboratory evaluation within the prior 10 years. He denied constipation, polyuria, confusion, depression, bone pain, and history of fractures or nephrolithiasis. Workup showed an inappropriately elevated PTH of 505 pg/mL (16-77 pg/mL). Neck ultrasound demonstrated a left inferior 3.9 cm complex thyroid nodule. Sestamibi scan confirmed increased uptake in the inferior left thyroid. Left neck exploration was performed. Intraoperatively, a 3.7 cm left parathyroid mass weighing 13.0 grams was encountered and excised in an en bloc fashion. The left superior parathyroid gland was evaluated and found to be normal. Intraoperative PTH level decreased from 529 pg/mL to 48 pg/mL 10 minutes after excision. Left hemithyroidectomy was not performed. Surgical pathology revealed PC with lymphovascular invasion, suspected capsular invasion, and negative margins. Immunohistochemical staining showed a Ki67 proliferation index up to 5% and complete loss of nuclear staining for parafibromin. Next generation sequencing demonstrated a somatic CDC73 p.L8fs mutation, tumor mutational burden 4.7m/MB, and stable microsatellite instability. Germline testing was negative for a CDC73 mutation. Postoperative staging did not demonstrate evidence of metastatic disease in the neck or chest. Serum Ca remained within normal limits. After multidisciplinary discussion, no further surgical intervention was recommended and plan was for ongoing biochemical and imaging surveillance. Conclusion: Though rare, PC should be considered as a cause of PHPT. The primary treatment is complete surgical resection. Unfortunately, there is a high rate of recurrence, >50%, with most occurring 2-5 years after initial surgery with a median overall survival of 14 years. Thus, long-term surveillance is of utmost importance. Treatment of recurrent disease is surgical resection when feasible as well as medical management of hypercalcemia. Further research is needed to better understand the role of targeted systemic therapy in addition to immunotherapy. PC is most commonly sporadic but can be hereditary, thus genetic evaluation is recommended. Given its rarity and complexity, PC is best managed in a multidisciplinary setting. Presentation: 6/1/2024

8409 Thyroid Nodules A to V: A Discussion on Thyroid Nodules and a Case Report of a Rare Thyroid Arteriovenous Malformation

Abstract Disclosure: M. Townsend: None. M. Brennan: None. C. Kazmierczak: None. P. Czako: None. Introduction: Thyroid nodules are an increasingly common finding on imaging, and the differential is broad. Arteriovenous malformations (AVMs) are a very rare cause of thyroid lesions, with only 6 reported cases to date. Given their scarcity, there is a lack of information regarding these lesions and how they are diagnosed and managed. Our case aims to address these gaps in information. Case: A 58-yo female with a history of hypertension was found by her PCP to have an enlarged left thyroid lobe with a new left sided bruit and palpable thrill. She had undergone prior thyroid ultrasonography for the enlarged left thyroid lobe which noted dilated and tortuous vascular structures at the posterior aspect of the left thyroid consistent with varices. These were being monitored clinically. Thyroid function tests were all normal. Due to concern for atherosclerotic disease, carotid ultrasound was obtained and showed patent carotid arteries with a large left sided thyroid mass. CTA of the neck revealed the mass to be a large (6.0 x 3.0 x 2.4 cm) AVM centered at the left thyroid gland. She underwent diagnostic angiography that confirmed the size of the mass and showed predominant arterial supply from the left superior thyroidal artery as well as bilateral inferior thyroidal arteries. Since the patient was asymptomatic with no reported neck pain, dysphagia or dyspnea, non-operative management with angioembolization was pursued given the risk of significant blood loss with surgical intervention. Following angioembolization, the results and adequacy of treatment are to be followed with repeat imaging given the high risk of reoccurrence. Discussion: AVMs of the thyroid are a very rare but clinically significant cause of thyroid lesions. Left untreated, they can grow in size and lead to compression of the esophagus or trachea, serious bleeding and high output heart failure. Their presentation is often non-specific and on routine thyroid imaging they can be difficult to differentiate from malignant tumors or varices, as in the case of our patient. Management prioritizes embolization, either alone or in conjunction with surgery, depending on the clinical scenario. Regardless of the treatment modality, reoccurrence rates remain high. Conclusion: Our case aims to add to the available information about thyroid AVMs and discuss the clinical presentation, challenges in diagnosis, imaging findings and treatment modalities available to manage these lesions. Presentation: 6/2/2024

12437 Impact Of Wearable Brain Sensing Meditation Device On Quality Of Life In Patients Recovering From Hypercortisolism Following Surgical Intervention: A Prospective Longitudinal Cohort Study

Abstract Disclosure: J. Saini: None. B. Bahrani Fard: None. M. Suresh: None. R. Sandooja: None. Y. Hleibiehova: None. E. Atkinson: None. S. Achenbach: None. I. Bancos: None. Background: Patients with endogenous hypercortisolism experience glucocorticoid withdrawal syndrome (GWS) following curative surgery. The symptoms of GWS include fatigue, weakness, muscle aches, joint pain, mood changes, and sleep disturbance. Limited interventions have been explored to alleviate the symptoms of GWS and improve patients’ quality of life. The use of meditation as an intervention has been reported to enhance postsurgical recovery in patients with other conditions and offers a promising intervention for GWS. Objective: To determine the impact of a portable, wearable, electroencephalographic device (MUSE headband device) used for guided meditation practices on the quality of life of patients in the first 12 weeks post-surgery for endogenous hypercortisolism. Methods: We conducted a single-center prospective longitudinal study of adults with endogenous hypercortisolism undergoing curative surgery between 2018 and 2024. The patients were enrolled before the surgical intervention and were followed for 2 years. Only patients who completed at least 4 weeks of follow-up were included. The study comprised of 2 groups; (1) The interventional group included consecutive patients who were offered a MUSE headband with instructions to meditate for at least 10 minutes per day for 3 months (MUSE cohort) and (2) the comparison group included age-, sex-, clinical score, hypercortisolism type, and BMI-matched 3:1 patients (Referent cohort). Quality of life and symptoms of GWS were assessed with AddiQoL and Short Form-36 (SF-36) surveys. Results: At least 4 weeks post-surgical follow-up was completed by 27 patients in the MUSE cohort and 81 referent subjects. Age (median 51 vs 47 years), women (82% vs 84%), BMI (median 31 vs 32 kg/m2), the subtype of hypercortisolism (pituitary 48% vs 52%), clinical (median 16 vs 15) and biochemical (median 6 vs 7) severity scores were similar between the two groups (P>0.05 for all). At baseline, AddiQoL score was similar in groups (median of 66 vs 70, P=0.083), though symptoms of fatigue (92.6% vs 69.1%, P=0.015) and lightheadedness (37% vs 17.3%, P=0.033) were more frequent in MUSE cohort. After 12 weeks, 20 patients using MUSE demonstrated improvement compared to 67 no muse patients in the SF-36 physical component (mean delta 3.9 (SD 11.77) vs -2.19 (SD 9.67), P=0.010). The physical functioning SF-36 subcomponent (4.94 (8.77) vs 0.92 (9.24), P=0.048) and body pain SF-36 subcomponent (2.69 (11.89) vs -3.69 (8.32), P=0.008) domains improved in the MUSE intervention group, when compared to referent cohort. No significant improvement in SF-36 mental component scores was seen in both groups. Conclusions: The use of wearable electroencephalographic device for meditation was associated with improvement in the quality of life of patients recovering from hypercortisolism, particularly in the domains of body pain and physical functioning. Presentation: 6/3/2024

6777 Exploring the comorbidity in males with 45,X/46,XY mosaicism unveils a pattern mirroring that of Turner syndrome

Abstract Disclosure: K. Stochholm: None. C.H. Gravholt: None. A. Berglund: None. Background: Males with 45,X/46,XY mosaicism are rare with an apparent prevalence of 6 per 100,000 newborn males. Knowledge about associated health outcomes are limited. Females with 45,X/46,XY fall under the Turner syndrome diagnosis but males do not. Aim: To investigate the comorbidity pattern in a national cohort of males with 45,X/46,XY. Methods: Morbidity were investigated using Cox regression analysis on administratively longitudinally collected registry data regarding hospital diagnoses, prescribed medication, and surgery codes. Data were retrieved for all males diagnosed with 45,X/46,XY from 1960 to 2018 (n=135) and for 13,500 age-matched males from the general population, who served as comparator. Results: 45,X/46,XY was associated an increased overall risk of receiving a hospital diagnosis (HR: 1.6, CI: 1.3-1.9), being prescribed medication (HR: 1.2, CI: 1.03-1.5), and undergoing a surgical procedure (HR: 1.8, CI: 1.4-2.1). Dividing hospital diagnoses into 18 chapters according to the International Classification of Diseases (ICD-10), 45,X/46,XY had a significantly increased risk of diagnoses in all but three chapters. Among diagnoses with a significantly increased risk were gonadal dysfunction (HR=63.7, CI: 34.8-116.9), short stature (HR=24.7, CI: 10.0-60.6), pubertal disorders (HR=25.8, CI:7.2-92.6), type 1 (HR=4.1, CI: 1.8-9.4) and type 2 diabetes mellitus (HR=3.4, CI: 1.7-6.6), thyroid disorders (HR=3.8, CI: 1.4-10.4), obesity (HR=4.4, CI: 2.3-8.2), osteoporosis and osteopenia (HR=5.4, CI: 2.4-12.3), hearing loss (HR=2.2, CI: 1.3-3.8), otitis media (HR=1.6, CI: 1.3-1.9), ischemic heart disease (HR=2.4, CI: 1.3-4.4), hypertension (HR=2.3, CI: 1.4-3.9), inflammatory bowel disease (HR=2.5, CI: 1.2-5.4), cryptorchidism (HR=11.9, CI: 7.8-17.8), hypospadias (25.9, CI: 14.0-47.8), testis cancer (HR=6.4, CI: 2.0-20.6), infertility (HR=23.5, CI: 16.0-34.4), gynecomastia (HR=4.6, CI: 1.7-12.5), horse shoe kidney (HR=177,8, CI: 16.1-1968.8), coarctation of the aortae (HR=66.0, CI: 11.0-394.9), and bicuspid aortic valve (HR=53.4, CI: 12.7-223.7). Conclusion: Males with 45,X/46,XY mosaicism exhibit heightened morbidity, evidenced by a notable surge in hospital diagnoses, prescribed medications, and surgical interventions. This increased morbidity is linked to a broad spectrum of diseases, showcasing a comorbidity pattern reminiscent of Turner syndrome. This study emphasizes the need for systematic follow-up in individuals with 45,X/46,XY mosaicism, highlighting the imperative for proactive healthcare management in this population. Presentation: 6/1/2024

6977 Unraveling Secondary Adrenal Insufficiency and an Invasive Pituitary Macroadenoma in a COVID-19 Positive Patient

Abstract Disclosure: F. El Sayed: None. A.A. Banka: None. Invasive pituitary macroadenomas extend into the extrasellar region and invade surrounding dural, periosteal, or mucosal tissues, often exceeding 1 centimeter and potentially compressing adjacent structures. Nonfunctioning pituitary adenomas (NFPAs), as they enlarge, can cause visual field impairment and ophthalmoplegia, with the decision for surgical intervention influenced by the degree of optic chiasm compression. NFPAs are sometimes associated with impaired endocrine function, particularly secondary adrenal insufficiency (sAI), which, warrants specific clinical attention. Management involves a combination of surgical interventions, such as transsphenoidal surgery, and medical approaches, including tailored hormone therapy or radiation therapy based on the tumor's characteristics. Clinical case: A 51-year-old female with a history of Sjogren's disease presented with a one-week duration of nausea, vomiting, diarrhea, and fatigue. Upon admission, she tested positive for COVID-19. Her vital signs indicated hypotension with a blood pressure in the 80s/40s range, a heart rate in the 90s, and she was afebrile on room air. Laboratory findings revealed significant hyponatremia (Na+ 118), K+ 4.3, HCO3- 19, and glucose 80. Workup for hyponatremia included a cortisol stimulation test, revealing secondary adrenal insufficiency with baseline cortisol of 3.5 ug/dl, 10.7ug/dl after 30 minutes, and 12.7ug/dl after 60 minutes. The patient denied exogenous steroid use, hypothyroid symptoms, polyuria, or polydipsia, and reported no headaches or visual symptoms. Endocrine evaluation showed hypogonadism despite post-menopausal status, with low estrone, estradiol, LH, and FSH levels. She was initiated on Cortef (hydrocortisone) with symptomatic improvement. Further investigation through an MRI revealed a large lobulated sellar mass measuring 3.2 x 2.8 x 3.5 cm compressing the optic chiasm and partially encasing the right internal carotid artery, leading to peripheral visual defects confirmed on perimetry. Following endoscopic endonasal pituitary macroadenoma resection, there was no evidence of interval growth on a one-year follow-up MRI scan. Discussion: The presented case highlights the importance of considering invasive pituitary macroadenomas in the differential diagnosis of patients with hyponatremia, particularly when accompanied by suggestive symptoms and an atypical cortisol response. The coexistence of COVID-19 adds a layer of complexity to the clinical scenario, necessitating a comprehensive approach to both infectious and endocrine management. Timely recognition, appropriate endocrine assessment, and targeted interventions, such as hydrocortisone replacement and surgical resection, are crucial for optimizing outcomes in patients with this intricate interplay of pituitary pathology and infectious states Presentation: 6/1/2024

7008 Challenges in the Management of Thyroid Lymphoma - Case Report

Abstract Disclosure: F. Toloza Bonilla: None. P. Veeraraghavan: None. R. Lakhotia: None. M. Roschewski: None. N. Nilubol: None. S. Gubbi: None. J. Klubo-Gwiezdzinska: None. Introduction: Primary thyroid lymphoma is an extremely rare thyroid malignancy accounting for less than 5% thyroid malignancies. The management depends on the histological subtype and tumor staging, typically involving chemotherapy alone or combined with radiotherapy. Although, surgical intervention is generally not recommended, given the potential surgical risks and the absence of additional benefits compared to chemoradiation therapy, it is reserved to obtain tissue diagnosis and to treat compressive symptoms. Clinical Case: A 66-year-old Caucasian female presented with dysphagia to solid food and acute neck swelling for a few weeks. History was negative for fever, weight loss or nocturnal diaphoresis. The patient had a history of primary hypertension, pre-diabetes, and Hashimoto’s hypothyroidism. A neck computed tomography (CT) scan showed a thyromegaly (8.3 x 5.8 cm) and bilateral cervical lymphadenopathy. Thyroid ultrasound showed sub centimeter nodules in the right mid-gland and a heterogeneous and irregular left thyroid lobe. TSH was normal (0.87 mcIU/mL [0.27-4.2]). She was treated for suspected subacute thyroiditis with prednisone for two weeks, showing initial clinical improvement, but symptoms recurred after steroids were stopped. Subsequently, a CT neck and fludeoxyglucose F18 (FDG) positron emission tomography (PET) scan demonstrated FDG avid thyroid enlargement with local adenopathy and rightward tracheal deviation. Lymph node, FNA, core biopsies and molecular testing were consistent with stage IIE MYC/BCL6 rearranged diffuse large B-cell lymphoma as she had no bone marrow or central nervous system (CNS) involvement. The patient’s treatments included four cycles of etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab with ibrutinib added after the first cycle and intrathecal methotrexate with cycles 3-6, to reduce the risk of CNS involvement. A 6-month post-therapy follow-up showed complete response (CR) on imaging with symptoms resolution. Four months later, she experienced worsening symptoms, including dysphagia with solids and liquids, and hoarseness despite CR to therapy and stable CT imaging. Laryngoscopic evaluation noted left vocal cord paralysis and extrinsic compression of the tracheoesophageal groove. Patient opted for a left hemithyroidectomy, experiencing excellent symptom relief. Surgical pathology showed findings consistent with a necrotic tumor and residual areas of lymphocytic thyroiditis. No active DLBCL was appreciated. The patient remains in remission and continues to be symptoms-free 24 months post-thyroid lymphoma treatment. Conclusion: While thyroidectomy is not typically recommended as the initial treatment for primary thyroid lymphoma, it emerges as a potentially effective option to manage recurrent or persistent compression symptoms following the completion of medical therapy. Presentation: 6/3/2024

5045 The Effects Of Non-functioning Adrenal Incidentalomas On Metabolic Comorbidities And Clinical Characteristics Changes: A Systematic Review And Meta-Analysis

Abstract Disclosure: X. Li: None. H. Lan: None. J. Wen: None. G. Chen: None. W. Lin: None. The Effects of Non-functioning Adrenal Incidentalomas on Metabolic Comorbidities and Clinical Characteristics Changes: A Systematic Review and Meta-analysis. Context: Adrenal incidentalomas (AI) are frequently detected during abdominal imaging, with non-functioning adrenal incidentalomas (NFAI) being particularly common, even in elderly individuals. This meta-analysis investigates the influence of NFAI on metabolic comorbidities, comparing non-surgical and surgical patient groups, and assessing alterations in NFAI characteristics. Design: Our comprehensive meta-analysis utilized data from multiple databases, encompassing studies from January 2000 to August 21, 2023.Setting: Data sources included PubMed, Embase, Cochrane Library, and Web of Science. Participants: The analysis comprises 24 articles involving 2,770 NFAI patients, categorized into non-surgical and surgical groups. Intervention: The non-surgical group underwent no surgery, while the surgical group underwent tumor resection. Main Outcome Measure: The study investigated changes in metabolic comorbidities (hypertension, diabetes, obesity, lipid metabolism disorders), tumor characteristics, and hormone production in NFAI patients during follow-up or after surgery. Results: In the non-surgical NFAI patient group (20 studies), metabolic comorbidities exhibited a discernible upward trajectory during follow-up. The initial hypertension prevalence of 58.3% increased by 4.2% over a 4-5 year follow-up period. Moreover, diabetes, obesity, and lipid metabolism disorders experienced significant increases of 5.8%, 2.2%, and 8.8%, respectively. In contrast, the surgical group (6 studies) demonstrated a notable reduction in hypertension, with 43.9% of initially hypertensive patients achieving hypertension-free status after surgery. As for tumor changes in the non-surgical group, they were generally inconsequential, with only 5% of patients witnessing tumor growth exceeding 10mm over approximately 3.3 years, and 8% undergoing functional changes. These findings underscore the divergent impact of non-surgical and surgical interventions on metabolic comorbidities in NFAI patients. Conclusion: The study advocates for regular monitoring of blood glucose and blood pressure in NFAI patients, especially those with metabolic comorbidities. When necessary, adenoma resection should be considered. Further investigation is warranted to elucidate the mechanisms connecting NFAI with metabolic factors. Presentation: 6/1/2024

12293 Dynamic Clinical Evolution: Why Patients Require Long-Term Follow-up Over Time

Abstract Disclosure: A. Attre: None. A. Syeda: None. A. Khan: None. B. Esayag-Tendler: None. Dynamic Clinical Evolution: Why Patients Require Long-Term Follow-up Over Time Introduction Primary Hyperaldosteronism (PHA) is an increasingly recognized cause of secondary hypertension amenable to specific therapy. We describe a case of PHA with change in management trajectory over time. Case A 48-year-old woman was diagnosed with PHA in 2009 based on an aldosterone level of 42.7 ng/dL, plasma renin activity of <0.1 ng/mL/hr, and a low potassium of 3.4 mmol/L. At that time, simultaneous adrenal venous sampling (AVS) had revealed a bilateral etiology of aldosterone excess. Original imaging with CT scan had shown fullness on both adrenal glands, and she was treated with 50mg daily spironolactone. Follow-up with CT scan in 2018 revealed similar imaging phenotype. When she established care with us in 2020, the abdomen MRI revealed a 2.5 cm x 1.9 cm right adrenal nodule. In addition, the blood pressure readings were noted to be high despite increasing doses of spironolactone to 150mg. Her laboratory results revealed aldosterone 151 ng/dL [< 31 ng/dL], cortisol 0.8 µg/dL, plasma renin activity 0.8 ng/mL/hr [0.2 ng/mL/hr - 1.6 ng/mL/hr], ACTH 12.5 pg/mL [7.2 pg/mL - 63.3 pg/mL], normal plasma metanephrine and a normal thyroid panel. A decision was made to repeat AVS in 2023 following Dr. Doppman’s protocol. The patient’s spironolactone was held before AVS and the plasma renin activity before the procedure was 0.4-0.8 ng/mL/hr. Results: Repeat AVS in 2023 showed mean pre-ACTH right to left lateralization index (LI) of 29.9 and mean post-ACTH LI of 9.7 (cutoff >4). This is concordant with the right adrenal nodule noted on imaging. The selectivity index confirmed adequate adrenal venous sampling data. Analysis of our findings confirmed right adrenal excess and left adrenal suppression compared to the IVC results. This patient underwent a laparoscopic right adrenalectomy in 2023. This patient's aldosterone levels were measured two days postoperatively and were found to be 4.2 ng/dL, showing immediate improvement. Six months postoperatively, our patient’s home and clinic blood pressures are in 120s/60s mmHg range without any medications. The aldosterone remains less than 6 ng/dL and the plasma renin activity is no longer low. Her potassium remains around 4.9 mmol/L. Discussion Based on current literature, surgical treatment is preferred when there is a confirmed unilateral cause of PHA. Adrenalectomy is recommended in patients with confirmed unilateral hyperaldosteronism especially when they do not achieve clinical and biochemical goals (renin plasma activity >1 ng/mL/hr, resolution of hypokalemia and optimal BP control) despite the use of MRA at appropriate doses. Suppressed renin is known to be associated with increased cardiovascular morbidity. This case serves as an important example of the need to follow patients long-term because PHA is a dynamic clinical entity that affects quality of life. Presentation: 6/3/2024

8617 Gender Differences In The Course Of Giant Prolactinomas - Single-Centre Case Series

Abstract Disclosure: M.A. Komisarz-Calik: None. A. Boguslawska: None. K. Ciszek: None. G. Zieliński: None. A. Hubalewska-Dydejczyk: None. A. Gilis-Januszewska: None. Introduction: Giant prolactinomas are the specific subtype of lactotroph PitNET, and are classified, according to their maximum diameter (≥40 mm). They constitute about 3% of prolactinomas. The prevalence is more common in men, however, the differences in the course of the disease between the genders remain unclear. Aim: The purpose of our study was to analyse gender differences in the course of giant prolactinomas. Materials and Methods: We analysed the data of consecutive patients with giant prolactinomas treated in the tertiary clinical center in the years 2022-2023. Results: There were 12 patients with giant prolactinoma (10 men and 2 women).Men and women were of similar age (32 vs 36 years). The maximum dimensions of the pituitary tumour in men were 56x70x67 mm, in women 60x55x55 mm. In all cases, treatment included dopamine agonists (cabergoline in 11 patients (all male patients and one female patient) and bromocriptine in one woman. Combined treatment with temozolomide and pasireotide were implemented in two male patients. In three men (30%) a surgical treatment was performed due to the visual field disturbances and severe headaches. Multiple surgeries were performed in two patients due to recurrence of symptoms and tumour progression (surgery was performed twice, and three times). One male patient received radiotherapy.The most frequent symptoms were associated with insufficiency of the adrenal, thyroid, and gonadal axis (80% vs 50%), visual field deficits (50% vs 50%) and headache (80% vs 0%), respectively in men and women. In men, the most common symptom was hypofunction of the gonadal axis (8 cases - 4 isolated gonadal axis hypofunction and 4 cases - hypofunction of the adrenal, thyroid and gonadal axis). In one woman, hypofunction of the three pituitary axes was present. Serum prolactin was higher in men than in women (6576 - 284232 ulU/ml vs 2000 - 5659 ulU/ml). In total, after treatment, prolactin concentration decreased in 7 cases, 5 men (50%) and 2 women (100%). The decrease in prolactin levels in men was by 80,4-99,9%, while in women it was by 83,9-86,7%. Tumour shrinkage was observed in 7 cases - 6/10 men and 1/2 woman. In men, tumour size was reduced by 27,5-64,4%. Tumour progression was observed in three cases, in 1 case the dimensions were stable. In two cases due to a recent diagnosis, follow-up MRI has not been yet performed. In women, tumour reduction by 99,8% was observed; in second the size of the tumour remained stable. Conclusions: The prevalence of giant prolactinomas is higher in men. The most frequent symptoms in both genders are visual field disturbances. The prevalence of tumour shrinkage is similar in both sexes, however giant prolactinomas require surgery more often in men. Further multicenter projects are needed to study the course of giant prolactinomas and to improve the outcomes of care. Presentation: 6/3/2024