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Background and Purpose Mechanical thrombectomy (MT) has become the standard of care for treatment of acute ischemic stroke secondary to large vessel occlusion up to 24 h from the last known normal time. With ADAPT and SOLUMBRA techniques, classically, a large bore aspiration catheter is delivered over a microcatheter and microwire crossing the clot to perform thrombectomy. Recently, a novel macrowire (Colossus 035 in.) has been introduced as a potential alternative to the use of microwire-microcatheter to allow the delivery of the aspiration catheter (ID = 0.070 in. up to 0.088 in.) over a macrowire alone. Objective To test the feasibility of delivering an aspiration catheter to clot interface over a macrowire alone. Materials and Methods A retrospective evaluation of prospectively maintained Macrowire for Intracranial Thrombectomy (MINT) Registry where this novel technique was utilized for thrombectomy. Consecutive patients undergoing MT using the MINT technique were included. We collected baseline demographics, imaging and clinical characteristics, rate of procedural success, conversion to traditional MT, and complications. Results Fifty consecutive patients were recruited during the initial 4 months of the larger study duration. The aspiration catheter was able to be advanced to the clot interface successfully in 46/50 (92%) using the MINT technique. Median time from vascular access to the first pass was 11.30 min (IQR = 7.45–14.30 min) and successful thrombectomy was 14 min (IQR = 10–22.15). The modified first-pass effect with this procedure was 71%. One vasospasm was reported as a procedural complication. Conclusions MINT is safe and feasible for large vessel occlusion recanalization based on our initial clinical experience in this multicenter study.

Abstract Objectives The impact of mild autonomous cortisol secretion (MACS) on cognition is incompletely characterized. We aimed to assess cognition in patients with MACS, identify factors associated with lower cognition, and determine the impact of adrenalectomy on cognition. Methods We conducted a cross-sectional study (4/2019 to 10/2022) and a longitudinal cohort study (10/2021 to 9/2023) of adults with MACS and referent subjects. Cognition was assessed with National Institute of Health Toolbox Cognition Battery and reported as standardized T scores (adjusted for age, sex, race/ethnicity, and education) for fluid, crystallized, and total composite cognition. Participants were assessed with urine steroid profiling (liquid chromatography-tandem mass spectrometry), frailty index, Beck’s Depression Inventory (BDI), and Short Form-36 (SF-36). Results A total of 84 patients (median age 57 years, 67% women) and 201 referent subjects (median age 63 years, 58% women) were included. Patients with MACS demonstrated lower mean (SD) total composite (50.9 [9.3] vs 55.4 [8.9], P < .001) and fluid composite T score (49.3 [10.6] vs 55.2 [10.2], P < .001), but not crystallized composite T score (52.3 [8.4] vs 54.0 [8.4], P = .130) when compared with referent subjects. Multivariable analysis adjusted for age, sex, BDI, SF-36, frailty index, total glucocorticoids, and androgens demonstrated that MACS status was associated with lower cognition. When cognition was reassessed in 37 patients post-adrenalectomy and 31 referent subjects, adjusted group differences of cognition change were similar except for a higher comparative increase in attention and executive functioning in patients with MACS. Conclusion Patients with MACS demonstrate lower cognition than referent subjects. Adrenalectomy for MACS had a minor positive impact on cognition.

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

Abstract Disclosure: J. Saini: None. R. Nathani: None. J. Larson: None. V. Fell: None. I. Bancos: None. Background: Surgical menopause due to bilateral salpingo-oophorectomy (BSO) at a younger age is associated with an increased risk of cardiovascular disease, cognitive decline, and increased mortality. Aging is associated with abnormalities in steroid metabolome, most notably an increased glucocorticoid to androgen ratio (“adrenal aging”). We hypothesized that in postmenopausal women of the same age, the duration of menopause is associated with adrenal aging. Objective: To determine the differences in the adrenal steroid metabolome of women with a history of BSO as compared to age-matched women following natural menopause. Methods: We conducted a single-center cross-sectional study in postmenopausal women with or without a history of BSO, between December 2020 to December 2022 Each participant collected 24-hour urine, which was analyzed for steroid profiling by liquid chromatography-tandem mass spectrometry (25 steroids). Exclusion criteria were inability to collect a 24h urine sample, exogenous glucocorticoid use, advanced malignancy, and chronic opioid use. Primary endpoints were glucocorticoid/androgen ratio, 11β-hydroxysteroid dehydrogenase type 2 activity (cortisol/cortisone, Tetrahydrocortisol (THF) + 5 α-tetrahydrocortisol (5 α-THF)/ Tetrahydrocortisone, THE) and 5 α-reductase type activity (Tetrahydrocortisol (THF)/5 α-tetrahydrocortisol (5 α-THF) and Etiocholanolone/Androsterone, Et/An). Results: A total of 245 women were enrolled: 124 women (median age of 66 years, IQR 63-72) with a history of BSO and 121 women (median age of 68 years, IQR 64-71) who underwent natural menopause (P=0.214). Median age at menopause was 44 years (IQR 41-46) in the BSO group, and 50 years (IQR 48-53) in the natural menopause group. History of hormone replacement therapy with estrogen was reported in 161 (66%) women, more frequently (92% vs 39%, P<0.001) and for a longer duration (median 12 years (IQR 6-16) vs 6 years (IQR 3-9), P<0.001) in in the BSO group, as compared to the natural menopause group. Although both groups had similar levels of urinary androgens (median 1387 vs 1686 mcg/24h, P=0.063) and total glucocorticoids (median 10877 vs 10277 mcg/24h, P=0.354), women with a history of BSO demonstrated a higher glucocorticoid/androgen ratio (median 7.9 (IQR 5.0-11.1) vs 6.7 (4.3-9.9), P=0.014), and a lower Et/An ratio (median 1.4 vs 1.6, P=0.045), but not THF/5aTHF ratio (median 1.7 vs 1.8, P=0.380) in comparison to women with natural menopause. No differences were found in other ratios. Conclusion: Women with a history of BSO demonstrated a higher glucocorticoid/androgen ratio in comparison to women undergoing natural menopause, suggestive of BSO-induced accelerated “adrenal aging”. Future studies need to examine associations between the abnormal steroid metabolome and increased cardiovascular morbidity, frailty, and mortality reported following BSO. Presentation: 6/3/2024

Abstract Disclosure: K. Yu: None. J. Saini: None. J.N. Farr: None. F. Vanessa: None. S. Khosla: None. I. Bancos: Advisory Board Member; Self; AstraZeneca, Adrenas, Neurocrine, Spruce, Recordati, Xeris, Novo Nordisk, HRA Pharmaceuticals, Sparrow, Diurnal, Corcept. Research Investigator; Self; HRA Pharmaceuticals, Recordati. Importance: Patients with both mild autonomous cortisol secretion (MACS) and overt Cushing syndrome (CS) demonstrated high prevalence of aging-related morbidity and an increased mortality. Objective: To determine whether p16INK4a in T cell, a cell cycle enzyme that associated with chronological aging and cell senescence, is associated with hypercortisolism and hypercortisolism-related comorbidities. Design, Setting, and Participants: In this single-center cross-sectional study, we prospectively recruited consecutive patients with hypercortisolism between July 1, 2020 and August 24 2022. Patients were included if they were diagnosed with Cushing syndrome (CS) or mild autonomous cortisol secretion (MACS). Age- (± 2 years) and sex-matched referent subjects without known adrenal disorders were included if abdominal imaging was available. Participants on exogenous glucocorticoids within 3 months prior were excluded. Exposure: Presence of hypercortisolism (MACS and CS). Main Outcomes and Measures: Primary outcomes included p16INK4a, advanced glycation end products (AGE) reader result, Frailty Index score, frailty (defined as frailty index>0.31), and physical performances in patients and matched referents at index date. Secondary outcomes included correlation between biological age markers, hormonal workup and the risk of comorbidities. p16INK4a expression analysis was adjusted for age, sex, smoking, and alcohol use for all analyses except for associations with CVD and frailty. Results: Of 85 patients (87% women, mean age 53 years), 51 (60%) had MACS (34 had matched referents), 34 (40%) had overt CS (16 had matched referents). Patients with CS demonstrated a median 1.9-fold higher p16INK4a expression (P<.001), and patients with MACS showed a median of 1.70-fold p16INK4a expression (P=.013), when compared to referent subjects. Age- and sex-adjusted p16INK4a expression was associated with frailty index score (r=0.23, P=.035), time-up-and-go test (r=0.28, P=.048), gait speed (r=-0.36, P=.035), but not with AGE reader result, 6-minute walk test, or hand grip measurement. The p16INK4a expression was associated with history of cardiovascular disease (age-adjusted odds ratio (aOR)=3.70, 95% confidence interval (CI), 1.20-11.43) and frailty (aOR=2.27, 95%CI, 1.04-4.98). Conclusion and relevance: We demonstrated evidence of cell senescence in both patients with CS and patients with MACS. Further studies need to determine the impact of surgical, cortisol-lowering, and senolytic medical therapies in MACS on cell senescence and associated aging-related comorbidities. Presentation: 6/1/2024

Abstract Disclosure: R. Sandooja: None. J. Saini: None. R. Gregg garcia: None. C. Zhang: None. S. Achenbach: None. E. Atkinson: None. J. Van Gompel: None. W.F. Young: None. I. Bancos: None. Hydrocortisone vs Prednisone During Recovery Following Surgical Cure for Endogenous Hypercortisolism: A Longitudinal Observational Study Introduction: Glucocorticoid withdrawal syndrome (GWS) is a constellation of symptoms that occurs after successful surgery for endogenous hypercortisolism. The objective of this study is to compare hydrocortisone versus prednisone on GWS symptoms. Methods: Study design: Single-center prospective longitudinal cohort study, 2019-2023. Participants: Adults with Cushing syndrome (CS) and mild autonomous cortisol secretion (MACS) with post-operative adrenal insufficiency treated with either hydrocortisone or prednisone for glucocorticoid replacement. Measurements: Clinical and biochemical severity scores for hypercortisolism were calculated. Quality of life (QOL) was assessed using Short Form-36 (SF-36) and Cushing QOL surveys. GWS was assessed using weekly AddiQoL surveys for the first 12 weeks after surgery. Results: Of 131 patients, 91 (69%) patients were treated with hydrocortisone and 40 (31%) with prednisone. No differences in age (median age 51 vs 53 years, P=0.62), sex (84 vs 85% women, P=0.83), etiology of hypercortisolism (ACTH-dependent: 44% vs 48%, P=0.26), clinical severity of hypercortisolism (median score 13 vs 12, P=0.97), or biochemical severity of hypercortisolism (median score of 6 in both, P=0.31) were noted between groups. When assessed at 4-, 8-, and 12-weeks post-surgery, the prevalence and trajectory of symptoms (fatigue, myalgias/arthralgias, sleep, headaches, nausea, weakness) were similar in patients treated with hydrocortisone and prednisone (P>0.05 for all). However, patients treated with prednisone were less likely to report mood changes (8.5% vs 20.9%, P= 0.004) compared to those treated with hydrocortisone. When compared to the presurgical baseline, the overall Cushing QOL score 12 weeks post-surgery improved in both groups (mean delta 8.9 vs 13.0, P=0.21). No differences in the hydrocortisone vs prednisone treatment were found in the SF-36 physical component score (mean delta of -1.7 vs 0.3, P=0.23) and SF-36 mental component score (mean delta 2.3 vs 5.0, P=0.22). Using multivariable analysis, age (estimate 0.22, P= 0.005), clinical severity score (estimate -0.73, P<0.001), female sex (estimate -5.45, P= 0.046) but not glucocorticoid type (estimate -0.06, P=0.98) were associated with the overall GWS symptom burden at 12 weeks. Conclusion: Use of prednisone after curative surgery for hypercortisolism was associated with lower mood symptoms, but did not impact the overall severity or trajectory of other symptoms associated with GWS. Baseline clinical severity of hypercortisolism, age, and female sex were associated with GWS burden. Presentation: 6/1/2024

Abstract Disclosure: B. Salama: None. J. Saini: None. V. Fell: None. E.J. Atkinson: None. S.J. Achenbach: None. Background: Mildly autonomous cortisol secretion (MACS) can be unilateral in 80% of cases, or bilateral in 20% of cases, due to either bilateral adrenal adenomas or bilateral macronodular adrenal hyperplasia. Scarce evidence demonstrates the differences in plasma steroid profiling of patients with bilateral versus unilateral MACS, however, these findings have not been confirmed using a more comprehensive 24h urine steroid profiling. Objectives: To characterize 24h urine steroid metabolome in patients with unilateral and bilateral MACS. Methods: We conducted a single-center cross-sectional study between 2019-2022. Eligible participants included consecutive patients with MACS who provided a 24h urine sample. Urine was analyzed for 25 steroids with a high-resolution mass spectrometry assay. MACS was defined as cortisol >1.8 mcg/dL following the overnight administration of 1 mg dexamethasone (DST-cortisol). Partial cohort analysis is presented. Results: Of 72 patients with MACS included in the interim analysis, 36 (50%) had bilateral MACS. The two groups (unilateral vs bilateral) were similar in age (median 58 vs 58 years), sex (women 67% vs 61%), BMI (median 33 vs 32 kg/m2), and menopausal status (36% vs 39%), P>0.05 for all. Prevalence of comorbidities was also similar in both groups: hypertension (89% vs 89%), hyperlipidemia (69% vs 78%), and hyperglycemia (69% vs 61%), P >0.05 for all. While the DST-cortisol (median 3.0 vs 3.2 mcg/dL, P= 0.51) and dehydroepiandrosterone sulfate (DHEAS) (median 37.5 vs 55.0, P = 0.21) were similar between the 2 groups, patients with bilateral MACS had a lower ACTH (median 12.4 vs 8.2 pg/mL, P = 0.012) when compared to patients with unilateral MACS. Median adrenal mass size was similar in patients with both unilateral MACS (2.7 cm, IQR 1.7-3.9) and bilateral MACS (3.0 cm, IQR 2.2-3.6) P = 0.54. Of the 25 steroids measured, only tetrahydrocorticosterone was higher in patients with unilateral MACS (median 245 mcg/24h, IQR 165-416 vs median 184 mcg/24h, IQR 121 -278) P = 0.039. No differences in androgens (median 2229 vs 2036 mcg/24h), cortisol metabolites (median 6566 vs 5191 mcg/24h), cortisone metabolites (median 10300 vs 9429 mcg/24h), or glucocorticoid/androgen ratio (median 7.9 vs 8.9) was demonstrated between the unilateral vs bilateral MACS groups (P>0.05 for all). Conclusion: In this interim analysis of patients with unilateral vs bilateral MACS, we have found that patients had a similar post-DST cortisol and similar tumor bulk. Despite a lower ACTH in patients with bilateral MACS, no differences in androgens were found between the two groups. In addition to expanding steroid profiling analysis to the whole cohort, subgroup analyses will need to distinguish between patients with bilateral adenomas and macronodular adrenal hyperplasia, consider aldosterone co-secretion, and employ a more accurate measurement of adrenal tumor bulk. Presentation: 6/3/2024

Abstract Disclosure: J. Saini: None. C.D. Zhang: None. V. Fell: None. E. Atkinson: None. S. Achenbach: None. I. Bancos: None. Background: Several studies employing computed tomography (CT) scans for body composition measurements have reported lower muscle mass and a higher proportion of visceral fat in patients with mild autonomous cortisol secretion (MACS) compared to referent subjects. While a CT scan assesses visceral adipose tissue (VAT) at a single slice level (L3), no studies have evaluated the overall VAT in patients with MACS using Dual-Energy X-ray absorptiometry (DXA). Objective: To determine the impact of MACS on VAT using DXA scan as compared to referent subjects. Methods: We conducted a single-center cross-sectional study of adults with 75 MACS and 75 referent subjects. MACS was defined as serum cortisol>1.8 mcg/dL after 1 mg dexamethasone suppression test in patients with adrenal adenomas and no features of overt hypercortisolism. Referent subjects were included if they had abdominal imaging and had no adrenal disorders. All the participants underwent a full body DXA scan between 04/2019 and 07/2022. We applied the CoreScan software to estimate the (1) total lean and fat mass (2) visceral fat mass and volume (3) lean android, fat android, and android mass, and compared measurements of patients and referent subjects using linear regression models adjusted for sex and BMI. Results: A total of 75 patients with MACS (median age 57.0 years, IQR 47.8-65.6, 67% women) and 75 referent subjects (median age 57.6 years, IQR 49.1-65.8, 67% women) were included. Patients had a higher BMI compared to referent subjects (median 31.7 kg/m2, IQR 27.4-37.9 vs 28.7, IQR, 25.4-33.8, P=0.004). The median post-DST cortisol in patients was 3.1 mcg/dL (IQR, 2.2-5.2). When compared to referent subjects, and after adjustment for sex and BMI, patients had a similar total body fat (estimate=846, p-value=0.28) and lean mass (estimate=-201, p-value=0.83), similar android fat mass (estimate=59, p-value=0.64) but lower gynoid fat mass (estimate=400, 0.007). Notably, sex and BMI-adjusted analysis also showed that patients had a higher VAT fat mass (estimate= -225, p-value=0.084) and a higher VAT fat mass/total mass ratio (estimate= -0.007, p-value=0.026). Conclusions: When adjusted for BMI and sex, patients with MACS do not demonstrate differences in overall fat and lean mass. However, we showed that MACS is associated with increased visceral adiposity, a known cardiovascular risk factor. Body composition assessment by DXA could be a safer and less expensive alternative in the evaluation and follow-up of patients with MACS. Presentation: 6/2/2024

Abstract Disclosure: M. Bassiony: None. P. Dogra: None. L. Šambula: None. J. Saini: None. U. Ambroziak: None. D. Kastelan: None. I. Bancos: None. Background: Frailty is characterized by a multi-system decline and increased vulnerability to adverse health outcomes. We have recently shown that patients with mild autonomous cortisol secretion (MACS) demonstrate a higher prevalence of frailty compared to patients with nonfunctioning adrenal adenomas (NFA). Objective: To determine the impact of adrenalectomy versus conservative management in patients with MACS, as compared to patients with NFA. Design: Multi-center, prospective cohort study (2019-2023). Methods: Adults with NFA and MACS were assessed for frailty at baseline and 1-year post-adrenalectomy, or conservative follow up. Frailty was assessed by frailty index (FI) that encompasses 47 health variables (comorbidities, symptoms, daily living activities). Patients with FI >0.25 were classified as frail. MACS was defined as post-dexamethasone cortisol>1.8 mcg/dL. Results: Paired frailty assessments were performed in 226 patients (MACS:117 and NFA:109). At baseline, patients’ median age was 63 years (interquartile range, IQR 55-78) and 113 (50%) were women, without differences between patients with MACS vs NFA. In conservatively treated patients with NFA (n=106) and MACS (n=61), baseline FI (median 0.15 vs 0.16, p=0.190) and frailty prevalence (18% vs 20%, p=0.846) were similar between groups. At follow up, patients with MACS demonstrated an increase in FI (mean of 0.013 vs -0.018 in patients with NFA, p=0.009). In conservatively treated patients, and after excluding outliers, post-dexamethasone cortisol positively correlated with a higher delta FI at follow up (estimate 0.015, p=0.01). Compared to conservatively treated, patients with MACS treated with adrenalectomy (n=56) were younger (median age of 58 vs 67 years, p=0.0002), had a similar post-dexamethasone cortisol (median 3.4 vs 2.8 mcg/dL, p=0.853), a higher FI (median 0.26 vs 0.15, p value <0.0001) and frailty prevalence (52% vs 20% P=0.0003) at baseline. At follow up, patients with MACS treated with adrenalectomy showed improved FI when compared to conservatively treated (mean delta FI of -0.025 vs 0.014, p=0.017). Conclusions: Patients with MACS treated conservatively demonstrate an accelerated frailty when compared to patients with NFA. In contrast, frailty improves in patients with MACS treated with adrenalectomy. Presentation: 6/2/2024

Abstract Disclosure: E.Y. Ferreira: None. J. Saini: None. J. Larson: None. E. Atkinson: None. C. Powell: None. S. Nevin: None. V. Fell: None. I. Bancos: Grant Recipient; Self; HRA Pharmaceuticals. Research Investigator; Self; HRA Pharmaceuticals. Context: Mild autonomous cortisol secretion (MACS) is the most prevalent hormonal abnormality demonstrated in 20-45% of patients with adrenal adenomas. MACS is associated with increased prevalence and incidence of cardiovascular morbidity, frailty, fragility fractures, psychiatric and sleep disorders, as well as increased mortality. Bilateral MACS due to bilateral adrenal adenomas or macronodular adrenal hyperplasia is seen in around 20% of patients with MACS. Management of patients with unilateral MACS who are not surgical candidates or do not desire adrenalectomy, and management of patients with bilateral MACS is challenging. Safe and effective medical therapy is urgently needed in these patients. Objective: 1) assess safety and tolerability of overnight metyrapone therapy in patients with MACS, 2) evaluate the impact of overnight metyrapone on steroid profiling and circadian cortisol secretion and 3) determine the efficacy of overnight metyrapone on metabolic and bone parameters, mood, sleep, cognition, quality of life, frailty and senescence biomarkers. Methods: This open-label, phase 2 interventional single-center study using overnight metyrapone opened for enrollment in December 2023 (NTC06106295) and plans to enroll 30 patients with MACS. Eligible participants include adults with adrenal adenoma or macronodular adrenal hyperplasia and MACS, and at least one comorbidity attributed to hypercortisolism. Metyrapone is administered overnight at 250 mg to 1000 mg. Duration of the study is 6 months (main study) and up to 42 months for extension study. Primary endpoint is incidence of treatment related adverse events. Key secondary endpoints include: glucocorticoid/androgen ratio, morning/evening cortisol curve, metabolic parameters (change in blood pressure, hyperglycemia, weight), frailty index and senescence biomarkers. Results: Between December 15th 2023 and April 6th, 7 patients with MACS (4, 57% women) enrolled at a median age of 62 years (IQR 56-68). Median BMI was 29 kg/m2(IQR 25-34). Post-dexamethasone cortisol was 3.1 mcg/dL (IQR 2.4-6.2), corticotropin (ACTH) was 7.3 pg/mL (IQR 5-20), and dehydroepiandrosterone-sulfate (DHEAS) was 73 mcg/dL (IQR 59-86). Median hypercortisolism clinical severity score was 9 (IQR 2-11) and biochemical severity score was 3.5 (IQR 2-5). Prevalence of hypertension (57%), dysglycemia (67%), dyslipidemia (86%), depression (57%), anxiety (43%), and bone disease (70%) was high. In 7 participants, median frailty index was 0.2 (IQR 0.2-0.4), and 3 (43%) were considered frail (frailty index >0.25). As of April 6th, 2024, no major treatment-related adverse events were reported, and no patient discontinued therapy. Conclusion: Results of this study will characterize safety and tolerability of overnight metyrapone in patients with MACS and evaluate the impact of overnight metyrapone on MACS-associated comorbidities. Presentation: 6/1/2024