Citations

Abstract Disclosure: R. Sandooja: None. A. Kittithaworn: None. P. Dogra: None. D. Gruppen: None. E. Atkinson: None. S. Achenbach: None. K. Yu: None. M. Connelly: None. V. Simha: None. R.P. Dullaart: None. I. Bancos: None. INTRODUCTION: Based on the spectrum of cortisol excess, adrenal adenomas are classified as adenomas with Cushing syndrome (CS), adenomas with mild autonomous cortisol secretion (MACS), and non-functioning adenomas (NFA). Patients with adrenal adenomas demonstrate a high prevalence of cardiovascular morbidity and mortality proportional to the degree of hypercortisolism. Evidence on whether dyslipidemia is a contributing cardiovascular risk factor in patients with NFA and MACS is discrepant. We aimed to characterize (apo) lipoprotein abnormalities across the spectrum of cortisol excess in patients with adenomas as compared to referent subjects. METHODS: Study Design: Single center cross sectional study between 01/2015 - 05/2021.Patients: Adults with NFA, MACS, or CS were consecutively enrolled. MACS was diagnosed based on post-dexamethasone cortisol >1.8 mcg/dL. Referent subjects were recruited from local population of patients with available abdominal imaging and no adrenal disorders. All subjects provided fasting ethylenediaminetetraacetic acid (EDTA) venous samples. Measurements: Nuclear magnetic resonance (NMR) spectroscopy measurements included total cholesterol (TC), low-density lipoprotein (LDL) and LDL particle concentrations, high-density lipoprotein (HDL) subclasses, apolipoprotein B (apo B), triglycerides (TG) and TG-rich lipoprotein concentrations. RESULTS: Participants included 101 patients with CS (median age 44 years, IQR 31-58, 85% women), 158 patients with MACS (median age 62 years, IQR 51-70, 62% women), 166 patients with NFA (median age 60 years, IQR 53--66, 63% women) and 136 referent subjects (median age 68 years, IQR 57-77, 52% women). Patients had higher BMI (32 vs 27 kg/m2), higher prevalence of hypertension (72% vs 46%) and diabetes mellitus (27% vs 9%) as compared to reference subjects. Statin therapy was used in 32% of patients and referent subjects. After adjusting for age, sex, BMI, smoking, diabetes, hypertension, and statin therapy, as compared to referent subjects, we found inconsistent increase in TC, LDL cholesterol and TG across CS, MACS and NFA and no consistent differences in LDL size, HDL variables, TG and TG-rich lipoproteins. However, when compared to referent subjects, LDL particle concentrations- CS(OR 1.78, 95% CI 1.33-2.39), MACS (OR 1.31, 95% CI 1.03-1.67), and NFA (OR 1.43, 95% CI 1.12-1.82) and Apo B levels were higher in all patient categories: CS (OR 2.26, 95% CI 1.57-3.24), MACS (OR 1.36 95% CI 1.00-1.85 ), and NFA (OR 1.54 95% CI 1.13-2.09). These differences were particularly evident in patients not on statin therapy. CONCLUSIONS: We found that LDL particle and Apo B concentrations were elevated in all patient groups, including those with MACS and NFA. In comparison to conventional lipid measurements, LDL particle and Apo B may serve as a better biomarker of the future cardiovascular risk in patients with adrenal adenomas. Presentation: Friday, June 16, 2023

Abstract Disclosure: S. Tella: None. J.C. Morris: None. M. Rivera: None. S. Gupta: None. M.M. Ryder: None. Introduction: NUT carcinoma is a rare subtype of squamous cell carcinoma defined by NUTM1 rearrangements encoding NUT-fusion oncoproteins with a very dismal prognosis. Recent data showed that NUTM1 rearranged carcinoma of the thyroid can mimic other thyroid primaries but NSD3-NUTM1 fusions aid in the diagnosis. Other than systemic chemotherapy with ifosfamide-based therapies and bromodomain inhibitors, therapeutic options for metastatic NUTM1 rearranged carcinoma of thyroid are limited. Herein, we describe a case of NUTM1 carcinoma of thyroid that had an impressive response to lenvatinib. Clinical case: We describe a case of a 41-year-old Caucasian male who presented to urgent care with acute onset aphonia and was eventually diagnosed with poorly differentiated thyroid carcinoma of size 4 x 4 cms extending into the internal jugular vein. He was managed with partial resection of the mass, internal jugular vein ligation, and a right select neck dissection. He had R2 resection due to possible vascular or airway invasion. As such, he received external beam radiation 70 Gy with 35 fractions with concurrent cisplatin followed by 200 mci radio-iodine therapy. The radiation therapy was complicated by the formation of a tracheo-esophageal fistula. A follow-up FDG-avid PET scan demonstrated residual thyroid bed disease and oligometastatic disease in bones. He received a couple of Stereotactic Body Radiation Therapy twice for bone lesions. Unfortunately, he had rapid disease progression with large pleural-based nodules and histology showed poorly differentiated thyroid carcinoma. NUT1 IHC stain was negative. We simultaneously obtained next-generation sequencing (NGS) and started him on lenvatinib 20 mg. Interestingly, NGS showed NSD3-NUTM1 fusions favoring the diagnosis of NUTM1 rearranged carcinoma of thyroid. He had an impressive partial response to lenvatinib within 4 weeks of initiation of lenvatinib and the response is sustained on 8-month follow-up. He tolerated lenvatinib reasonably without any unexpected complications. In an event of progression, we intend to consider a clinical trial, chemotherapy in combination with bromodomain inhibitors, or another anti-angiogenic tyrosine kinase inhibitor therapy. Conclusions: We noticed an impressive and sustained partial response in NUTM1 rearranged carcinoma of thyroid with anti-angiogenic multi-kinase inhibitor, lenvatinib opening new avenues of targeted therapy in the therapeutic landscape of NUT1 carcinomas. Importantly, NUT1 stain could be negative and NGS is the gold standard for accurate diagnosis. Although our study is limited by one case report, we hope that by highlighting the spectrum of this disease that more cases will be recognized, facilitating risk stratification and improved treatment, and further enabling future studies to explore the clinical management and biology of NUTM1 rearranged carcinoma of thyroid. Presentation: Thursday, June 15, 2023

Abstract Disclosure: A. Blinder: None. K. Nanba: None. D. Sapiro: None. J. Baker: None. C. Liu: None. I. Bancos: None. M. Lyden: None. W. Young: None. H. Wachtel: None. D. Cohen: None. J. Luther: None. T.A. Williams: None. M. Reincke: None. T. Else: None. T.J. Giordano: None. A. Udager: None. W.E. Rainey: None. Background: There is accumulating evidence that changes in adrenal histology and regulation of renin-angiotensin-aldosterone system occur with age. Primary aldosteronism (PA) is the most common cause of endocrine hypertension. Recent clinical studies suggest unique characteristics of PA in elderly patients, including high prevalence of comorbidities and low clinical cure rate after adrenalectomy. However, histologic and genetic features of PA in late adulthood have not been well elucidated. Objective: To determine histologic and genetic characteristics of PA in late adulthood. Methods: Seventy-six patients who underwent unilateral adrenalectomy at the age of 60 or older were included in this study. Formalin-fixed, paraffin-embedded (FFPE) sections of resected adrenal tissue were used for the analysis. Aldosterone synthase (CYP11B2) immunohistochemistry (IHC) was performed to identify the source of inappropriate aldosterone production. Histologic classification was made according to the HISTALDO (histopathology of primary aldosteronism) consensus. CYP11B2 IHC-guided DNA capture followed by sequencing analysis using direct Sanger sequencing or ion torrent based next-generation sequencing (NGS) was performed. Results: Median age of the studied patients was 70 (interquartile range: 64-73). Based on the CYP11B2 IHC, histologic diagnosis was made as follows; aldosterone-producing adenoma (APA, n=23), aldosterone-producing nodule (APN, n=41), and non-functioning adrenocortical adenoma (NFA, n=6). The remaining six cases had multiple CYP11B2-expressing neoplastic lesions, including APA with APN (n=2) and multiple APNs (n=4). Co-existence of NFA with APA or APN(s) was also observed in 13. Sequencing analysis revealed that somatic KCNJ5 mutation was the most frequent genetic alteration in APA (7/23, 30%), whereas somatic CACNA1D mutation was the most common genetic cause of APN (20/39 with successful sequencing, 51%). Of the 18 sequenced NFA DNA samples, two had somatic mutations in CTNNB1 (n=1) and GNAS (n=1). Conclusion: APN is the major histologic feature of PA in late adulthood. Co-existence of NFA also appears to be a frequent observation in this age population. Somatic CACNA1D and KCNJ5 mutations are common in APN and APA, respectively. Presentation: Friday, June 16, 2023

Abstract Disclosure: M. Chinthapalli: None. P. Dogra: None. R. Sandooja: None. L. Rahimi: None. N.M. Iniguez Ariza: None. T. Foster: None. I. Bancos: None. Introduction: Adrenal glands are susceptible to hemorrhage due to their unique vasculature and physiological stress response. Scarce data are available on the presentation, etiology, and outcomes of adrenal hemorrhage (AH). Objective: To describe the presentation, etiological associations, and outcomes of patients with unilateral and bilateral AH. Methods: Single-center retrospective longitudinal study of consecutive patients reported to have AH on imaging performed between January 1st 2017-December 31st 2021. Clinical, baseline and follow up imaging, and laboratory data were reviewed. Subgroup analysis was performed based on the laterality (unilateral vs. bilateral) of AH. Results: Of 454 patients with AH (median age 62 years (IQR 50-70), 160 (35%) women), 383 (85%) had unilateral AH, 60 (13%) presented with synchronous bilateral AH, and 9 (2%) had unilateral AH followed by contralateral AH at a later time (metachronous bilateral AH). Only 93 (20%) patients had an evaluation by an endocrinologist. AH was discovered incidentally in 190 (42%) patients, and during evaluation for abdominal or back pain in 133 (29%), trauma in 104 (23%), sepsis in 19 (4%), and adrenal insufficiency in 8 (2%). Primary etiology of AH was a post-procedural complication in 154 (34%), trauma in 126 (28%), coagulopathy in 54 (12%), anticoagulant or antiplatelet therapy in 52 (12%), adrenal neoplasm in 29 (6%) and sepsis in 20 (4%). Metastasis (15, 50%) represented the most common adrenal neoplasm associated with AH. In 208 (46%) patients, diagnosis of AH occurred in the hospital setting, and in 246 (54%) during an outpatient evaluation. In the 393 patients with available baseline imaging, the median size of AH was 3.1 cm (IQR 2.2-4.0). During a median imaging follow-up of 6 months (IQR 3-12), AH reduced in size with a median decrease of -2.6 cm (IQR -1.8 to -3.7) on the right and -2.0 cm (IQR -1.0 to -4.8) on the left. Compared to patients with unilateral AH, those with bilateral AH were more likely to be diagnosed in the hospital setting (61 vs. 43%, P=0.006), have an underlying coagulopathy (50 vs. 4%, P<0.0001), or sepsis (13 vs. 3%, P<0.0001), be on anticoagulant or antiplatelet therapy (48 vs. 21%, P<0.0001), develop primary adrenal insufficiency (61 vs. 0%, P<0.0001) and have larger baseline AH size (4 cm vs. left 2.7 and right 3.1 cm, P=0.0002), but a similar rate of resolution. Conclusions: AH frequently presents as unilateral hemorrhage and can occur secondary to various etiologies, with trauma and postprocedural complication being the most common. Association with an underlying adrenal mass is uncommon, seen only in 6%. Bilateral AH carries a high risk for primary adrenal insufficiency and is more likely to occur in hospitalized patients, possibly due to an increased prevalence of underlying coagulopathy, sepsis and need for anticoagulation or antiplatelet therapy. Presentation: Friday, June 16, 2023

Abstract Disclosure: S.H. Johnson: None. C. Zhang: None. P.T. Hangge: None. T.W. Yen: None. T. Shaik: None. K. Doffek: None. J.W. Findling: None. T.B. Carroll: None. D.B. Evans: None. S. Dream: None. T.S. Wang: None. Background: Secondary adrenal insufficiency (SAI) may occur in patients after unilateral adrenalectomy for adrenal-dependent hypercortisolism (HC) and/or primary aldosteronism (PA). Perioperative protocols include routine glucocorticoid replacement (GR) or selective GR based on postoperative day 1 (POD1) basal cortisol levels or cosyntropin stimulation testing (CST). This study aimed to assess if a POD1 basal cortisol level alone was predictive of an abnormal CST and the need for GR in patients following unilateral adrenalectomy for HC and/or PA. Methods: This is a single institution retrospective review of consecutive unilateral adrenalectomies performed for HC and/or PA from 9/2014-10/2022. Patients were grouped as overt hypercortisolism (OH;n=42), mild autonomous cortisol excretion (MACE;n=70), mixed PA/HC (n=22) or PA (n=73); 22 patients with PA did not have preoperative evaluation for HC. Preoperative morning cortisol after low-dose dexamethasone suppression testing (DST), was used to define MACE (1.8-4.9 µg/dL) and OH (≥5.0). POD1 CST was performed for all patients with HC and prior to 2021, all patients with PA. SAI was defined as basal cortisol ≤5 or stimulated ≤14 (≤18 before 4/2017). Receiver operating characteristic (ROC) curves and sensitivity analyses were performed to assess the sensitivity (SN) and specificity (SP) of cutoffs within the range of observed basal cortisol levels in predicting an abnormal CST and need for GR. Results: Of 207 patients, 152 had POD1 CST (93% OH, 96% MACE, 73% PA/HC, 41% PA). Of these, 80 (53%) had SAI (67% OH, 55% MACE, 44% PA/HC, and 33% PA). Of the 10 patients with PA and SAI, 5 did not have preoperative testing for HC. Overall, 81 patients were discharged on GR. Median (interquartile range [IQR]) duration of GR was 246 (127,557), 55 (38,207), 74 (16,185), and 26 (15,36) days in patients with OH, MACE, PA/HC, and PA, respectively. At a median follow-up of 142 days (IQR 42,617), 12 patients (5 OH, 6 MACE, 1 PA/HC) remained on GR. The SN/SP of a basal cortisol ≤10 in predicting GR was 92%/77% in patients with OH and 94%/73% of patients with MACE. Compared to initiation of GR based on basal cortisol ≤10, CST identified 4 patients with SAI in the combined OH and MACE cohorts who would not have received GR, and 11 in the combined cohort who did not require GR. For patients with PA and PA/HC, a basal cortisol ≤10 had SN of 100% and SP of 85% and 67%, respectively. The optimal basal cortisol for predicting SAI in patients with PA/HC was ≤5 (SN,SP 100%). Area under the curve for all ROC curves was >0.9. Conclusion: These results demonstrate that in patients who underwent unilateral adrenalectomy for HC, PA, or mixed PA/HC, POD1 CST improved identification of patients at risk for SAI compared to basal cortisol levels alone. While basal cortisol levels alone may be considered in patients with PA or mixed HC/PA, all other patients with HC should have POD1 CST to determine need for postoperative GR. Presentation: Friday, June 16, 2023

Abstract Disclosure: K.N. Rachmasari: None. P. Thapa: None. D. Sighoko: Employee; Self; Horizon Therapeutics. L. Abdul Jabbar: None. M.N. Stan: None. Objective: To describe the epidemiology of Thyroid Eye Disease (TED). Methods: A population-based cohort of all Olmsted County, Minnesota, residents who had newly diagnosed TED between April 3, 2002, and December 31, 2021, was identified through the medical diagnostic index of the Rochester Epidemiology Project. Individuals aged 18 years and older were included. Incidence rates and point prevalence were calculated. Results: We identified 137 incident patients, of whom 124 (90.5%) were female (p < 0.0001). The overall incidence was 6.24 cases/100,000 person-years in Olmsted County, corresponding to 6.25 cases/100,000 person-years for the US population (age and sex adjusted incidence). Women had higher incidence (10.94 cases/ 100,000 person-years) compared to men (1.22 cases/100,000 person-years). The distribution of incidence rates by ten-year age groups demonstrated peak incidence rates in the age groups 70 to 79 years (17.94 cases/100,000 person-years for women compared with 4.04 cases for men). The majority of cases (77/137) occurred between 50-79 years of age. No clear trend was identified for the yearly incidence between 2002 and 2021. The overall estimated point prevalence per 100,000 was 65.6 (95% CI, 57.8 – 72.9). Prevalence was 117.6 (95% CI, 96.5 – 141.4) for females and 11.2 (95% CI, 5.1 – 21.2) for males (p < 0.0001). Conclusions: Incidence rates for TED remained stable and significant over the last 2 decades. Majority of disease burden is present after the age of 50 with the peak between 70-79 years, a decade later than in the previous study from our population (1). Based on reported incidence and prevalence of Graves’ disease (2), our data indicates that TED continues to affect about 20-30% of that population and appropriate resources should be devoted to furthering education, management, and research into this condition. References: 1. Bartley GB, Fatourechi V, Kadrmas EF, et al. The incidence of Graves' ophthalmopathy in Olmsted County, Minnesota. Am J Ophthalmol 1995;120(4):511-7, doi:10.1016/s0002-9394(14)72666-2 2. Hussain YS, Hookham JC, Allahabadia A, et al. Epidemiology, management and outcomes of Graves' disease-real life data. Endocrine 2017;56(3):568-578, doi:10.1007/s12020-017-1306-5 Presentation: Friday, June 16, 2023

Abstract Disclosure: S. Bjornsdottir: None. W. Kamal: None. B.L. Langdahl: None. T. Spelman: None. B.L. Clarke: None. O. Kampe: None. Context: Previous studies have shown that patients with hypoparathyroidism (hypoPT) have reduced bone remodeling, with consequent increases in bone density, and abnormalities in microarchitecture and bone strength. It is still not clear whether there is an increased risk of fractures in patients with hypoPT. Objective: The aim of this study was to evaluate the risk of fractures in patients with hypoPT in Sweden. Patients: The Swedish National Patient Register, the Swedish Prescribed Drug Register and the Total Population Register were used to identify 1982 patients with chronic hypoPT (duration ≥ 12 months), and 19820 controls matched by age, sex and county of residency between 1997-2018. The 10th revision of the International Classification of Diseases (ICD) was used to identify fractures. Results: Patients with hypoPT did not have higher risk of any fracture compared to controls (HR 0.96; 95% CI 0.86-1.08). However, patients with hypoPT had a slightly higher risk of vertebral fractures (HR 1.33; 95% CI 1.01-1.75), p= 0.047 and a lower risk of femoral fractures (HR 0.60; 95% CI 0.45-0.82), p= 0.001. There was no significant difference in the risk of fractures of the forearm, p= 0.177, proximal humerus, p= 0.096 or pelvis, p= 0.446. There was no difference in the risk of any fracture between females and males with hypoPT (p for interaction= 0.511). Patients with surgical hypoPT had a significantly higher risk of any fracture compared with patients with non-surgical hypoPT (p for interaction= 0.006). Conclusion: The risk of any fracture was not increased in patients with hypoPT. However, the risk of vertebral fracture was increased, and the risk of femoral fracture was lower than for matched controls. No difference was found in fracture risk between females and males. Patients with surgical hypoPT had a higher fracture risk compared to patients with non-surgical hypoPT. Presentation: Saturday, June 17, 2023

Abstract Disclosure: S. Mohan: None. M.T. Sheehan: None. P.J. Tebben: None. R.A. Wermers: None. Introduction: Elevated 1,25-dihydroxyvitamin D (1,25(OH)2D) is a rare cause of non-parathyroid hormone (PTH) mediated hypercalcemia. An increase in the activating enzyme 1-alpha hydroxylase is seen in granulomatous diseases and lymphoma, while mutations in the CYP24A1 gene leads to reduced catabolism of 1,25(OH)2D. Cinacalcet has been shown to successfully treat 1,25(OH)2D-mediated hypercalcemia of malignancy. Extrapolating this, we report 3 patients with non-malignant 1,25(OH)2D-mediated hypercalcemia treated with cinacalcet. Case Series: The patients (2 male and 1 female) were 55-71 years old. At presentation to our clinic, all had hypercalcemia with serum calcium concentrations between 10.6-11.5 mg/dL (normal, 8.8-10.2 mg/dL). PTH ranged between 16-35 pg/ml (normal 15-65 pg/ml), PTH-related peptide was normal in all patients, 25-hydroxyvitamin D was 32-51 ng/ml, and 1,25(OH)2D was inappropriately normal between 31-77 pg/ml (normal 18-78 pg/mL) in the setting of hypercalcemia and chronic kidney disease in 2 patients with estimated glomerular filtration rates 35-42 ml/min. Other causes of hypercalcemia including sarcoidosis, tuberculosis and malignancy were ruled out. The female patient had hypercalciuria (288 mg/24 hours) without nephrolithiasis and both male patients had severe hypercalciuria (400-660 mg/24 hours) with recurrent nephrolithiasis. One male patient had biallelic variants in the CYP24A1 gene, while the other male patient was suspected to have similar mutations, but not identified on genetic testing. The female patient with a PTH of 35 pg/mL on our initial measurement had documented 1,25(OH)2D level of 82 pg/mL with PTH <20 pg/mL while previously hypercalcemic. Upon cinacalcet initiation all patients demonstrated normalization of calcium levels (8.6-9.5 mg/dl) with doses between 30-90 mg daily. The patient with CYP24A1 gene mutations experienced symptomatic hypocalcemia with calcium of 8.1 mg/dL requiring dose reduction and eventual discontinuation of cinacalcet due to limited clinical benefit. There were no consistent changes in 24-hour urine calcium or fractional excretion of calcium. Levels of 1,25(OH)2D increased and PTH decreased on cinacalcet while serum calcium levels were maintained within normal range, including 2 subjects with continued normocalcemia after 2 years of therapy. Conclusion: Cinacalcet may be a therapeutic option in non-malignant 1,25(OH)2D-mediated hypercalcemia. Further evaluation is needed to confirm efficacy, understand risks and benefits, and elucidate potential mechanisms of action. Mild decrease in PTH may lead to reduced skeletal calcium efflux while the maintenance of normocalcemia despite rising 1,25(OH)2D, which was also seen in our reported patients with malignant 1,25(OH)2D-mediated hypercalcemia, suggests cinacalcet may decrease intestinal calcium absorption. Presentation: Saturday, June 17, 2023

Abstract Disclosure: S. Maraka: None. R. Owen: None. N.M. Singh Ospina: None. M. Knox: None. T. Dodds: None. H. Spencer: None. A. Albashaireh: None. A. Shah: None. S. Syed: None. S. Naqvi: None. H. Motahari: None. S. Thumma: None. E. Ambrogini: None. J.P. Brito: None. Objective: Levothyroxine (LT4) therapy has not been shown to improve quality of life (QoL), thyroid-related symptoms, cardiovascular events, or mortality for patients with subclinical hypothyroidism (SCH) in clinical trials. We conducted this pilot, double-blind, placebo-controlled clinical trial to evaluate the effects of LT4 discontinuation among adults with SCH. Methods: We aimed to randomize 50 adults 1:1 to continue receiving LT4 (25-75 mcg/day) for SCH or discontinue it (switch to placebo). The primary outcome was feasibility. Secondary outcomes included changes in QoL measures (Thyroid-specific QoL Patient-Reported Outcome [ThyPRO]-Hypothyroid Symptoms and Tiredness scores, EuroQoL 5-Dimension Self-Report Questionnaire [EQ-5D]) assessed at baseline and 6 months post-randomization, and incidence of adverse events (overt hypothyroidism, hyperthyroidism, atrial fibrillation, stroke, acute coronary syndrome, heart failure, fracture, mortality). Higher scores for ThyPRO indicate more symptoms and tiredness and for EQ-5D, better health state. Data are reported as mean (standard deviation). Analysis of covariance model adjusting for age and baseline measure of the variable was performed for the outcomes based on the intention-to-treat principle. Results: Fifty participants were enrolled (33% recruitment rate); 24 were randomized to the LT4 and 26 to the discontinuation group. Five patients were excluded post-randomization due to lack of ascertainment of SCH diagnosis (final N=45; 21 LT4, 24 discontinuation). There was no statistically significant difference at baseline between the discontinuation and LT4 groups in age [65.7 (10.6) vs. 71.0 (7.9) yrs], gender (male 75 vs. 86%), LT4 dose (25 mcg; 29.2 vs. 33.3%, 50 mcg; 54.2 vs. 47.6%, 75 mcg; 16.7 vs. 19.0%), TSH [3.1 (1.0) vs. 3.2 (1.4) mIU/L], TPOAb positivity (17 vs. 19%), ThyPRO-Hypothyroid Symptoms [27.1 (20.4) vs. 21.1 (18.4)] and Tiredness score [33.2 (23.7) vs. 31.1 (23.9)], and EQ-5D [0.746 (0.229) vs. 0.758 (0.193)]. A patient in the discontinuation group withdrew for personal reasons (98% completion rate). Two patients in the discontinuation group met study criteria to restart LT4 (TSH>10 mIU/L; n=1, fatigue; n=1). At final visit, 34.8% of patients in the discontinuation group had mild SCH compared to 9.5% of patients on LT4 (p=0.07). There was no statistically significant difference between the discontinuation and LT4 groups in ThyPRO-Hypothyroid Symptoms [28.3 (22.8) vs. 22.9 (19.5)], Tiredness [27.6 (22.8) vs. 32.8 (22.1)], and EQ-5D score [0.750 (0.232) vs. 0.741 (0.180)]. A patient suffered rib fracture (placebo); no other adverse event of interest was reported. Conclusion: This pilot clinical trial showed the feasibility and safety of discontinuing LT4 in patients with SCH. These findings support proceeding with a larger multi-site clinical trial to fully assess the effects of LT4 discontinuation. Presentation: Thursday, June 15, 2023

Abstract Disclosure: J. Saini: None. R. Nathani: None. C. Zhang: None. M. Suresh: None. K. Thangamuthu: None. S. Singh: None. V. Fell: None. E.J. Atkinson: None. S. Achenbach: None. N.H. Stricker: None. I. Bancos: None. Background: Patients with mild autonomous cortisol secretion (MACS) have impaired cognition compared to patients with non-functioning adrenal adenomas. However, the impact of adrenalectomy on cognitive function in patients with MACS is unclear. Objective: To determine the impact of adrenalectomy on cognitive function in patients with MACS. Methods: Single-center prospective longitudinal study of adults with MACS. MACS was defined as serum cortisol >1.8 mcg/dL after the 1 mg dexamethasone suppression test (DST) in patients with adrenal adenomas without any overt features of hypercortisolism. Patients underwent cognitive evaluation using the standardized National Institute of Health (NIH) Toolbox Cognition Battery (7 tests of attention, episodic and working memory, language, executive function, cognitive flexibility, and processing speed) prior to adrenalectomy and at follow-up at least 10 months post-surgery. Fully corrected T-scores for age, sex, education, and race were compared using a paired t-test before and after adrenalectomy. A T-score of 50 is average performance (SD of 10). Total cognition is composite of fluid cognition (executive function, episodic memory, cognitive flexibility, working memory and processing speed) and crystallized cognition (language and vocabulary). Results: A total of 27 patients with MACS (median age 59.7 years, IQR 51.4-66.9, 17, 63% women) underwent cognitive evaluation prior to and at a median of 1.5 years (IQR, 1.1- 2.0) after adrenalectomy. Before surgery, median post-DST cortisol was 3.8 mcg/dL (IQR, 2.7-6.4) mcg/dL. Of the 27 patients, 21 (78%) patients developed post-operative adrenal insufficiency with 6 (21%) patients still requiring still requiring glucocorticoid replacement at the time of the last follow-up. At baseline, the mean total composite T-score was 50.7 (9.3), with fluid composite T-score of 49.9 (9.4) and crystallized composite T-score of 51.3 (8.7). Following adrenalectomy, all three composite T-scores improved compared to baseline. The crystallized composite T-score (composed of language and vocabulary) increased by a mean of 3.7 (5.5), P=0.001, the fluid composite T-score (composed of episodic, executive, working memory, cognitive flexibility, and processing speed) increased by a mean of 3.1 (8.3), P=0.068, and the total composite T-score improved by a mean of 3.9 (6.2), P=0.004. Conclusion: We showed that adrenalectomy in patients with MACS is associated with improvement in cognition. However, as test results may improve with practice (i.e., improvement due to taking the test the second time), to determine whether the improvements observed represent a reliable change in cognition, the next step is to evaluate for cognition score changes in referent subjects. Presentation: Friday, June 16, 2023