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OBJECTIVE Malignant melanotic nerve sheath tumors are rare tumors characterized by neoplastic melanin-producing Schwann cells. In this study, the authors report their institution’s experience in treating spinal and peripheral malignant melanotic nerve sheath tumors and compare their results with the literature. METHODS Data were collected from 8 patients who underwent surgical treatment for malignant melanotic nerve sheath tumors between 1996 and 2023 at Mayo Clinic and 63 patients from the literature. Time-to-event analyses were performed for the combined group of 71 cases to evaluate the risk of recurrence, metastasis, and death based on tumor location and type of treatment received. Unpaired 2-sample t-tests and Fisher’s exact tests were used to determine statistical significance between groups. RESULTS Between 1996 and 2023, 8 patients with malignant melanotic nerve sheath tumors underwent surgery at the authors’ institution, while 63 patients were identified in the literature. The authors’ patients and those in the literature had the same mean age at diagnosis (43 years). At the authors’ institution, 5 patients (63%) experienced metastasis, 6 patients (75%) experienced long-term recurrence, and 5 patients (62.5%) died. In the literature, most patients (60.3%) were males, with a peak incidence between the 4th and 5th decades of life. Nineteen patients (31.1%) were diagnosed with Carney complex. Nerve root tumors accounted for most presentations (n = 39, 61.9%). Moreover, 24 patients (38.1%) had intradural lesions, with 54.2% (n = 13) being intramedullary and 45.8% (n = 11) extramedullary. Most patients underwent gross-total resection (GTR) (n = 41, 66.1%), followed by subtotal resection (STR) (n = 12, 19.4%), STR with radiation therapy (9.7%), and GTR with radiation therapy (4.8%). Sixteen patients (27.6%) experienced metastasis, 23 (39.7%) experienced recurrence, and 13 (22%) died. Kaplan-Meier analyses showed no significant differences among treatment approaches in terms of recurrence-free, metastasis-free, and overall survival (p > 0.05). Similar results were obtained when looking at the differences with respect to intradural versus nerve root location of the tumor (p > 0.05). CONCLUSIONS Malignant melanotic nerve sheath tumors are rare tumors with a high potential for malignancy. They carry a dismal prognosis, with a pooled local recurrence rate of 42%, distant metastasis rate of 27%, and mortality rate of 26%. The findings from this study suggest a trend favoring the use of GTR alone or STR with radiation therapy over STR alone. Mortality was similar regardless, which highlights the need for the development of effective treatment options to improve survival in patients with melanotic schwannomas.

AbstractA robust and heterogenous secretory phenotype is a core feature of most senescent cells. In addition to mediators of age‐related pathology, components of the senescence associated secretory phenotype (SASP) have been studied as biomarkers of senescent cell burden and, in turn, biological age. Therefore, we hypothesized that circulating concentrations of candidate senescence biomarkers, including chemokines, cytokines, matrix remodeling proteins, and growth factors, could predict mortality in older adults. We assessed associations between plasma levels of 28 SASP proteins and risk of mortality over a median follow‐up of 6.3 years in 1923 patients 65 years of age or older with zero or one chronic condition at baseline. Overall, the five senescence biomarkers most strongly associated with an increased risk of death were GDF15, RAGE, VEGFA, PARC, and MMP2, after adjusting for age, sex, race, and the presence of one chronic condition. The combination of biomarkers and clinical and demographic covariates exhibited a significantly higher c‐statistic for risk of death (0.79, 95% confidence interval (CI): 0.76–0.82) than the covariates alone (0.70, CI: 0.67–0.74) (p < 0.001). Collectively, these findings lend further support to biomarkers of cellular senescence as informative predictors of clinically important health outcomes in older adults, including death.

Abstract Disclosure: M. Moazzami: Grant Recipient; Self; Rochester Epidemiology Project. S. Achenbach: None. E. Atkinson: None. I. Bancos: None. Background: Epidemiology of adrenal insufficiency (AI) is incompletely characterized with most data originating from referral centers and registries. We aimed to determine the incidence, morbidity index, risk of hospitalizations, and mortality in patients with AI living in Olmsted County, Minnesota. Methods: We assessed the standardized incidence rate, morbidity index, risk of hospitalizations and mortality of AI in residents (aged 18+) in Olmsted County, MN, USA, from Jan 1, 2005, to December 31, 2021. The data was collected using the Rochester Epidemiology Project (REP), a database of medical records for all Olmsted County residents since 1966. Incidence rates were standardized for age and sex according to the 2020 US white population. Sex- and age- matched referent subjects were selected from the REP. AI was defined based on presence of oral chronic glucocorticoid therapy (hydrocortisone, prednisone, prednisolone, or dexamethasone) defined as (1) any hydrocortisone use or (2) 6 months of consecutive use of prednisone, prednisolone, or dexamethasone or (3) two AI diagnosis codes 6+ months apart plus at least one glucocorticoid prescription within 1 year of the second diagnosis. Elixhauser morbidity index was used. Findings: Between 2005 and 2021, 5419 patients were diagnosed with AI (median age of 62 years, range 18-103), 56% women). Overall standardized incidence rates for AI increased from 206 (95% CI 174-238) in 2005 to 252 (223-280) per 100 000 person-years in 2021. At baseline, patients with AI had a higher morbidity index (median 3 vs median 1, p &lt;0.001) and a higher history of hospitalizations within 5 years prior to baseline (57% vs 30%; p&lt;0.001) when compared to referent subjects. When comparing patients with AI to referent subjects, and after adjusting for age, sex, morbidity index and prior history of hospitalizations, patients with AI were more likely to be hospitalized during follow-up (aHR 1.4, 95% CI 1.3-1.5). When comparing patients with AI to referent subjects, and after adjusting age, sex, and morbidity index, patients with AI had higher mortality (aHR 1.7, 95% CI 1.6-1.9). Patients with AI demonstrated a higher risk of dying from musculoskeletal disorders (aHR 4.9, 95% CI 2.2-10.8), respiratory disorders (aHR 4.7, 95% CI 3.3-6.6), neoplasms (aHR 2.4, 95% CI 2.0-2.9), and infectious disorders (aHR 2.3, 95% CI 1.2-4.3) than referent subjects. Interpretation: We demonstrate an increase in AI incidence between 2005 and 2021. Surprisingly, even after controlling for morbidity and prior hospitalizations, patients with AI were more likely to be hospitalized. In comparison to referent subjects, mortality was higher in patients with AI, even after adjustment for morbidity index. Presentation: Friday, June 16, 2023

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 &gt;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: 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 &gt;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

Abstract Disclosure: C.D. Zhang: None. S. Singh: None. J. Saini: None. M. Suresh: None. K. Thangamuthu: None. R. Nathani: None. A.L. Ebbehøj: None. V. Fell: None. S.J. Achenbach: None. E.J. Atkinson: None. S. Khosla: None. I. Bancos: None. Background: Patients with mild autonomous cortisol secretion (MACS) have higher rates of fractures compared to patients with non-functioning adrenal nodules, but bone mass is typically only modestly reduced. We hypothesized that chronic exposure to mild levels of cortisol excess may lead to a deterioration in bone quality. Objective: To characterize the effect of MACS on bone metabolism and bone microarchitecture, as measured by high-resolution peripheral quantitative computed tomography (HR-pQCT). Methods: In this cross-sectional single-center study, patients with MACS were matched by age, sex, and gonadal status to referent subjects without adrenal nodules. MACS was defined as serum cortisol concentration &gt;1.8 mcg/dL after the 1 mg overnight dexamethasone suppression test (1-mg DST), in the absence of a classic Cushingoid phenotype. Those with other known secondary causes of osteoporosis and/or on pharmacologic treatment for low bone mass were excluded. All study participants underwent a bone health interview, blood draw for bone turnover markers, dual-energy x-ray absorptiometry (DXA) scan with trabecular bone score (TBS), and HR-pQCT of the non-dominant radius and tibia. Participants with a recent fracture within 12 months were excluded from the analysis of bone turnover markers. The Kruskal-Wallis test was used to compare measurements between groups. Results: A total of 82 patients with MACS and 82 referent subjects were prospectively enrolled between 1/2019 and 7/2022. The median age of study participants at the time of enrolment was 57 years (interquartile range [IQR], 47-65), and 57 (70%) were women. In the MACS cohort, the median cortisol following 1-mg DST was 3.2 mcg/dL (IQR, 2.3-6.5) with median ACTH of 8.7 pg/mL (IQR, 6.0-14.0) and median DHEA-S of 42.0 mcg/dL (IQR 23.0-68.0). While no differences in bone mineral density (BMD) were observed at any site (lumbar spine, total hip, femoral neck, or distal radius) between the two groups, patients with MACS had decreased TBS (1.374 vs 1.467, P &lt;0.001) and lower osteocalcin concentrations (16.9 vs. 19.7 ng/mL, P = 0.005) than referent subjects without adrenal nodules. On HR-pQCT at the tibia, patients with MACS had significantly reduced trabecular volumetric BMD (151.6 vs 167.4 mg hydroxyapatite/cm3, P = 0.002), trabecular bone volume/tissue volume ratio (0.219 vs 0.237, P = 0.011), and number of trabeculae (1.428 vs 1.506 1/mm, P = 0.045), while trabecular separation (0.707 vs 0.656, P = 0.023) was increased compared to referent subjects. Conclusions: Patients with MACS have altered bone metabolism and microstructural deterioration that is not evident on routine DXA BMD testing. These changes may mediate their increased fracture risk and could serve as biomarkers of cortisol-induced changes in the bone. Presentation: Thursday, June 15, 2023

Abstract Disclosure: J. Saini: None. R. Nathani: None. S. Singh: None. V. Fell: None. E. Atkinson: None. S. Achenbach: None. S. Khosla: None. I. Bancos: None. Background: Previous studies reported that both cortisol secretion and bone metabolism biomarkers follow a circadian pattern of secretion. Patients with mild autonomous cortisol secretion (MACS) demonstrate an increased risk of fractures. As most patients with MACS do not have increased cortisol production, we hypothesized that abnormal circadian cortisol secretion is associated with impaired bone metabolism. Objective: To compare the circadian secretory pattern of bone metabolism biomarkers in relation to cortisol circadian secretion in patients with MACS versus referent subjects. Methods: We conducted a pilot cross-sectional study of patients with MACS and referent subjects. MACS was diagnosed in patients with adrenal adenomas based on an abnormal 1 mg dexamethasone suppression test (cortisol &gt;1.8 mcg/dL). Referent subjects with available abdominal imaging within 5 years and adrenal disorder were recruited from the community. Participants were admitted to the clinical research unit for blood sampling every 2 hours over 24h period. Measurements included total and free cortisol, calcium, parathyroid hormone (PTH), osteocalcin, amino-terminal propeptide type 1 collagen (PINP), and carboxy-terminal telopeptide of type 1 collagen (CTX). Subjects with disorders or medication affecting bone metabolism were excluded. Time periods of blood draw were categorized into the morning (6 to 12 hours), afternoon (14-18 hours) and night (20-2 hours). Delta (morning measurements/afternoon measurements) was calculated. Results: Subjects included 12 patients with MACS (median age 57, IQR 48-67, 83% women) and 10 referent subjects (median age 57, IQR 50-63, 80% women). The 24-hour area under the curve for total (10342 vs 9090 mcg/dL, p=0.468) and free cortisol (437 vs 329 mcg/dL, p=0.086) was no different between patients with MACS and referent subjects. However, the mean night total (6.7 vs 4.3 mcg/dL, p=0.056) and free cortisol (0.2 vs 0.1 mcg/dL, p=0.035) was higher in MACS vs referent subjects. The area under the curve for calcium, phosphorus, CTX, osteocalcin and PINP were similar between patients and referent subjects, however, the area under the curve for PTH was higher in patients vs referent subjects (mean 64179 vs 42602 pg/mL, p=0.021). Both delta total cortisol (mean 8.6 vs 5.5, p=0.01) and delta PTH (mean -1.5 vs 4.2, p=0.051) was higher in referent subjects vs patients with MACS. Conclusion: When compared to referent subjects, patients with MACS have similar 24-hour cortisol production but demonstrate an increase in night-time cortisol secretion and a blunting of diurnal cortisol (lower morning/afternoon cortisol). Patients with MACS have higher PTH production overall, as well as an abnormal diurnal PTH secretion. Noted abnormalities in PTH may contribute to the MACS-associated impairment in bone health. Presentation: Thursday, June 15, 2023

Abstract Disclosure: J. Saini: None. R. Nathani: None. S. Singh: None. K. Thangamuthu: None. M. Suresh: None. C. Zhang: None. A.L. Ebbehøj: None. M. Thomas: None. V. Fell: None. E. Atkinson: None. S. Achenbach: None. N. Stricker: None. I. Bancos: None. Introduction: While patients with overt Cushing syndrome are reported to have impaired cognition, the impact of milder, long-standing hypercortisolism on cognition is incompletely characterized. Objective: To determine the impact of MACS on cognition as compared to age, sex, and education-matched referent subjects. Methods: We conducted a single-center cross-sectional study of adults with MACS and referent subjects. MACS was defined as serum cortisol&gt;1.8 mcg/dL after 1 mg dexamethasone suppression test (DST) in patients with adrenal incidentalomas. Referent subjects were included if they had abdominal imaging and had no adrenal disorders. Exclusion criteria were malignancy and exogenous glucocorticoid use within 1 year. All participants underwent a cognitive evaluation using the NIH Toolbox Cognition Battery between 1/2019 to 7/2022. NIH Toolbox assesses 8 cognitive domains using 7 tests and yields 3 composite scores: fluid cognition (executive function, episodic memory, cognitive flexibility, working memory, and processing speed), crystallized cognition (language and vocabulary), and total composite cognition (composite of all). Results are given in fully corrected T scores (adjusted for age, sex, race, and education) with an average of 50 and a standard deviation (SD) of 10. A subgroup analysis was performed based on DST cortisol. The Kruskal-Wallis test was used to compare scores between groups. Results: A total of 94 patients with MACS (median age 57.2 years, IQR 47.8-66.5, 70% women) and 94 referent subjects (median age 58 years, IQR 49.1-66.4, 70% women) were included. The median post-DST cortisol in patients with MACS was 3.3 mcg/dL (IQR, 2.4-6.2). The mean (SD) total composite T-score was lower in patients with MACS vs referent subjects (51 (9.1) vs 56.3 (9.3), P&lt;0.001). Patients with MACS demonstrated lower mean fluid composite T-score when compared to referent subjects (49.5 (10.4) vs 56.9 (9.7), P&lt;0.001). However, mean crystallized composite T-scores were similar in patients with MACS and referent subjects (52.3 (8.1) vs 53.9 (9.6), P=0.342). A subgroup analysis of patients with post-DST cortisol &lt;3 mcg/dL (n=40) vs patients with post-DST cortisol &gt;3 mcg/dL (n=54) did not show any differences in the total, fluid, or crystalized composite scores. Conclusion: Patients with MACS demonstrate lower cognitive performances than a referent group suggesting MACS has a subtle impact on cognitive functioning. The pattern of cognitive impairment in patients with MACS is similar to that seen with normal cognitive aging: impaired fluid cognitions and unaffected crystallized cognition). Cognitive performance did not differ based on the degree of MACS suggesting that in the absence of overt features of hypercortisolism, the degree of MACS is less important than the presence of MACS. Presentation: Thursday, June 15, 2023

Abstract Disclosure: D.Z. Erickson: None. D. Donegan: None. J. Van Gompel: None. J. Atkinson: None. M. Link: None. F. Meyer: None. M. Peris-Celda: None. G. Spears: None. J. Bornhorst: None. M. Hoplin: None. Dysnatremias are common after neurosurgical procedures. Depending on the cohort assessed, transient arginine vasopressin deficiency (AVD) following neurological procedures is seen in up to 46% of patients which can delay discharge. Copeptin (COPEP), a stable surrogate marker of arginine vasopressin, has demonstrated utility in the prediction of postoperative AVD, however COPEP cutoff and sample timing has varied. Aim: To assess the optimal sampling time and cut point concentration of COPEP to predict the development of post-surgical AVD. Method: Adults who had transsphenoidal surgery (TSS) for a sellar or suprasellar mass between February 2020 and April 2022 without pre-existing AVD were prospectively enrolled if agreeable. Two COPEP samples (immunofluorescent assay on B.R.A.H.M.S Kryptor Compact PLUS) included “early” sample 1-6 hours following extubation, and another post-op day 1 (POD1, 10-30 hours of extubation). Patients were assessed for the development of AVD; defined as new onset hypotonic (&lt; 295 mmol/kg) polyuria (&gt;50 ml/kg/d) without other causes. Patient demographics and tumor characteristics were collected. Results: 192 patients (median age 54.5 (39.8-67.0) years with 54.2% female) were included. Surgical indications included non-functioning pituitary adenoma (N=101), functioning pituitary adenoma (N= 78), disorders or the craniopharyngeal duct (N=10) and other (N=3). Median COPEP levels were associated with age, but not sex. Median COPEP levels were significantly lower at both time points in patients who developed AVD (N=20, 10.4%) vs those who did not, (early: 4.9 vs 18.7 pmol/L, P= &lt;0.001; POD1: 3.35 vs 4.9 pmol/L, P=&lt;0.001). Change in median COPEP level between the 2 sample times was lower in those who developed AVD -1.8 pmol/L vs who did not -12.6 pmol/L (P&lt;0.001). ROC curve analysis of early COPEP indicated that a level &gt;20.3 pmol/L had a negative predictive value (NPV) of 97% whereas POD1 level &gt;6.7 pmolL had a NPV of 96%. In univariate logistic analysis, lower early COPEP was associated with higher risk of AVD (OR=0.34, CI 0.26 -0.62, p=0.008), with an optimal cut point of 8.5 pmol/L. A similar association was seen for POD1 COPEP (OR=0.19, CI 0.07- 0.53, p= 0.002), which had an optimal cut point of 4.3 pmol/L. In patients with disorders of the craniopharyngeal system vs those who had TSS for other reasons, AVD was more common (60% vs 9%, P&lt;0.001) and median COPEP levels were lower at both time points. Those without AVD who received stress dose steroids intraoperatively had lower median early COPEP (11.7 vs 19.1 pmol/L, P=0.27). Conclusion: In early samples taken following extubation, the optimal COPEP cut point for AVD diagnosis was 8.5 pmol/L and a level of &gt;20.3 pmol/L has predicative utility in excluding AVD. However, caution should be used in patients who are administered glucocorticoids intra-operatively as this was associated with a lower median COPEP level. Presentation: Thursday, June 15, 2023

Abstract Disclosure: L. Rahimi: None. A. Kittithaworn: None. R. Gregg Garcia: None. J. Saini: None. P. Dogra: None. E. Atkinson: None. S. Achenbach: None. A. Kattah: None. I. Bancos: None. Objective: Patients with mild autonomous cortisol secretion (MACS) have been reported to have a higher prevalence of chronic kidney disease (CKD), possibly due to the direct effect of hypercortisolism on kidney function and indirect effect of MACS-associated cardiovascular comorbidities, such as diabetes, hypertension, obesity, and dyslipidemia. Limited studies suggest improvement of kidney function following adrenalectomy in patients with MACS. In this study, we aimed to assess the factors associated and the degree and timing of change in kidney function post adrenalectomy in patients with MACS or nonfunctioning adrenal adenoma (NFA). Methods: We conducted a retrospective single-center study and included adult patients with MACS or NFA diagnosed based on a post-dexamethasone cortisol cutoff of 1.8 mcg/dL, who underwent adrenalectomy between 1999-2022. The change in estimated glomerular filtration rate (eGFR) before and up to 3.5 years after adrenalectomy was defined as the primary outcome. Demographics and comorbidities were included in univariable and multivariable analyses. Results: We included 155 (76.0%) patients with MACS and 49 (24.0%) patients with NFA treated with adrenalectomy. The proportion of women was high in both MACS and NFA (71.6% vs 69.4%, p=0.77), however, patients with MACS were older (median age 59.2 vs 54.6 years in NFA, p=0.05). The prevalence of hypertension was higher in MACS vs NFA (71.0% vs 53.1%, p=0.02), while the prevalence of diabetes (25.2% vs 28.6%, p=0.89), dyslipidemia (47.7% vs 46.9%, p=0.92), smoking (74.2% vs 68.9%, p=0.49) and obesity (median BMI 30.4 vs 31.8 kg/m2, p=0.35) was similar between the two groups. Prior to adrenalectomy, patients with MACS had lower eGFR (median 84.4 vs 89.2 ml/min/1.73m2, p=0.09) and a higher prevalence of CKD stage ≥ 3 (16.1% vs 8.2%, p= 0.16). In patients with MACS, after an initial decline of eGFR within 6 months post adrenalectomy (mean decrease 5.3 ml/min/1.73m2), eGFR increased by a mean of 4.9 points at 18-30 months, and by a mean of 8.1 points at 30-42 months post-adrenalectomy (p&lt;0.01). Patients with NFA followed a similar eGFR change trend (p=NS). When comparing post-adrenalectomy delta eGFR in patients with MACS vs NFA, no significant differences were found. After adjusting for age, sex, pre-adrenalectomy eGFR, patient group, hypertension, antihypertensive therapy, and diabetes, there were still significant changes in eGFR over time. In a multivariable analysis, younger age (est -031, p&lt;0.001) and lower pre-adrenalectomy eGFR (est-0.27, p=0.001) were associated with kidney function improvement post-adrenalectomy. Conclusion: Patients with MACS and NFA demonstrate improvement of eGFR over the 3.5 years of follow up post-adrenalectomy. The factors that are associated with improvement of eGFR are lower eGFR before surgery, younger age at time of adrenalectomy and longer follow up post adrenalectomy. Presentation: Friday, June 16, 2023