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Zhang, Catherine D

https://orcid.org/0000-0003-2784-2673

Mayo Clinic

Mayo Clinic

Citations 25

Impact of mild autonomous cortisol secretion on bone density, metabolism, and microstructure: a cross-sectional study
Zhang, Catherine D , Saini, Jasmine, Singh, Sumitabh , Suresh, Malavika, Thangamuthu, Karthik, Nathani, Rohit, Ebbehøj, Andreas , Fell, Vanessa , Achenbach, Sara J, Atkinson, Elizabeth J. , Khosla, Sundeep , Bancos, Irina , Ebbehøj, Andreas Ladefoged , Fell, Vanessa , Saini, Jasmine , Suresh, Malavika, Thangamuthu, Karthik, Nathani, Rohit , Achenbach, Sara J., Khosla, Sundeep , Bancos, Irina

The Journal of Clinical Endocrinology & Metabolism | April 15, 2026 | Volume: No volume available | Issue: No issue available | Pages: No page available

10.1210/clinem/dgag175 Get It

Abstract Context Patients with mild autonomous cortisol secretion (MACS) have higher rates of vertebral fractures compared to patients with non-functioning adrenal nodules, yet bone density is not always reduced. Objective To characterize the effect of MACS on bone density, metabolism, and microstructure as measured by high-resolution peripheral quantitative computed tomography (HR-pQCT). Design Cross-sectional study, 2019-2022 Setting Tertiary referral center Participants Seventy-five patients with MACS and 75 age-, sex-, and gonadal status–matched referent subjects. Measurements Bone turnover markers, dual-energy x-ray absorptiometry (DXA) scan, and HR-pQCT. Outcomes Areal and volumetric bone mineral density (aBMD, vBMD), trabecular bone score (TBS), microstructural parameters including trabecular bone volume to total volume (BV/TV) ratio. Results While no differences in aBMD were observed at any skeletal site, patients with MACS had decreased TBS (1.389 vs 1.475, P < .001) and lower osteocalcin concentration (17.1 vs 19.5 ng/mL, P = .030) than referent subjects. On HR-pQCT at the tibia, patients with MACS had reduced trabecular BV/TV (0.220 vs 0.233, P = .015) compared to referent subjects. On multivariable analysis, MACS was associated with lower TBS (odds ratio [OR] per SD decrease 2.87 [1.65-5.00]), lower trabecular BV/TV at the radius (OR per SD decrease 2.58 [1.33-5.00]), and lower trabecular BV/TV at the tibia (OR per SD decrease 4.06 [2.10-7.86]). Conclusion Patients with MACS have microstructural deterioration that may not be evident on routine DXA aBMD testing.
Bone Health in Patients With Adrenal Adenomas and Hypercortisolism: A Multicenter Cross‐Sectional Study
Šambula, Lana, Athimulam, Shobana , Tsagarakis, Stylianos , Vassiliadi, Dimitra A. , Antonopoulou, Vasiliki , Nathani, Rohit , Zhang, Catherine D , Genere, Natalia , Ambroziak, Urszula , Hubska, Joanna , Salama, Bahaa , Atkinson, Elizabeth J. , Fell, Vanessa , Larson, Joseph J. , Zhang, Catherine D , Garcia, Raul G , Bassiony, Mohamed, Kastelan, Darko , Bancos, Irina , Ambroziak, Urszula , Dogra, Prerna , Saini, Jasmine , Drake, Matthew T. , Garcia, Raul Gregg , Bassiony, Mohamed A. A. , Kaštelan, Darko , Bancos, Irina

Clinical Endocrinology | October 8, 2025 | Volume: 104 | Issue: 2 | Pages: 103-112

10.1111/cen.70048 Get It

ABSTRACT Objective Data on bone health in patients with mild autonomous cortisol secretion (MACS) are limited and heterogenous. We sought to assess the prevalence of osteoporosis and symptomatic fragility fractures in patients with adrenal adenomas and hypercortisolism, and explore associations with the degree of cortisol excess and frailty. Design This multicenter cross ‐sectional study involved prospective enrollment of adults with nonfunctioning adrenal adenomas (NFA), MACS, Cushing syndrome (CS) and referent subjects without adrenal disorders during the study period (January 2019–September 2022). All participants completed a bone health questionnaire at enrollment and had dual‐energy X ‐ray absorptiometry bone mineral density assessment within 12‐months. Final analyses were adjusted for age, sex, body mass index, smoking status, alcohol use. Results Participants included 117 with NFA (median age 62 years, 80% women), 191 with MACS (median age 63 years, 74% women), 62 with CS (median age 50 years, 92% women), and 101 referent subjects (median age 59 years, 47% women). Both patients with CS (OR: 3.0, 95% CI: 1.1–8.3) and MACS (OR: 2.2, 95% CI: 1.9–4.9) had a higher prevalence of osteoporosis when compared to referents. Among patients with MACS, only those with post 1‐mg dexamethasone suppression test (post‐1mg‐DST) cortisol > 83 nmol/L had a higher prevalence of osteoporosis when compared to referents (OR: 3.2, 95% CI: 1.4–7.5) and NFA (OR: 2.2, 95% CI: 1.1–4.4). For clinical fragility fractures, only patients with CS showed an increased prevalence when compared to referents (OR: 6.1, 95% CI: 1.7–26.4) and NFA (OR: 3.8, 95% CI: 1.3–11.2). Prevalence of clinical fragility fractures was similar to referents in patients with MACS (OR: 1.8, 95% CI: 0.6–6.9) and NFA (OR: 1.5, 95% CI: 0.4–6.1), and was not associated with post‐1mg‐DST cortisol or frailty in the MACS and NFA groups. Conclusion Patients with CS, and those with MACS and post‐1mg‐DST cortisol > 83 nmol/L, exhibited a higher burden of osteoporosis. However, only CS was associated with an elevated risk of symptomatic fragility fractures.
Cortisol Testing to Diagnose Adrenal Insufficiency Following Adrenalectomy for Mild Autonomous Cortisol Secretion
Hamidi, Oksana , Salama, Bahaa , Findling, James W. , Zhang, Catherine D , Dream, Sophie , Balderrama-Brondani, Vania , Dackiw, Alan P.B., Mirfakhraee, Sasan , Mehta, Ankeeta , McKenzie, Travis J. , Foster, Trenton R. , Findling, James W , Balderrama-Brondani, Vania , Mirfakhraee, Sasan , Foster, Trenton, Bancos, Irina , Hamidi, Oksana , Wang, Tracy S. , Carroll, Ty B , Sada, Alaa , Dogra, Prerna , Oltmann, Sarah Catherine , Bancos, Irina

The Journal of Clinical Endocrinology & Metabolism | September 12, 2025 | Volume: 111 | Issue: 3 | Pages: 665-678

10.1210/clinem/dgaf515 Get It

Abstract Context Patients with mild autonomous cortisol secretion (MACS) can develop adrenal insufficiency after unilateral adrenalectomy. Objective This work aimed to determine the prevalence, duration, and predictors of adrenal insufficiency, and compare postoperative basal cortisol and cosyntropin stimulation test (CST). Methods In this multicenter retrospective study of patients with MACS, adrenal insufficiency was diagnosed when postoperative basal cortisol was less than 10 µg/dL and/or CST < 18 µg/dL. The results were concordant when both tests met cutoffs. Biochemical (BSS) and clinical severity scores (CSS) were calculated. Results Among 281 patients with MACS (80% women), postoperative adrenal insufficiency was diagnosed in 153 (54.5%) patients. Adrenal insufficiency inversely correlated with age (odds ratio [OR] 0.67 per 10 years; 95% CI, 0.53-0.84). Low basal cortisol and CST were associated with younger age (OR 0.64 per 10 years for both) and higher BSS (OR 1.17 and 1.22, respectively). Basal cortisol and CST were discordant in 22% of patients, and the discordance rate was more common in patients with bilateral nodules (32% vs 19%; P < .001). The median time to adrenal insufficiency recovery was 3.9 months (IQR, 3-5.9 months), with longer duration associated with higher BSS and CSS: 3 months for mild, 4 to 5 months for moderate, and 12 to 14 months for severe BSS and CSS. Conclusion Approximately half of patients with MACS developed postoperative adrenal insufficiency, with 50% recovering by 3.9 months after surgery. BSS correlated with basal cortisol, CST, and duration of adrenal insufficiency. As discordant results were noted in 22%, performing both basal cortisol and CST postoperatively should be considered.
Impact of hydrocortisone vs prednisone therapy on postsurgical recovery in patients with endogenous hypercortisolism: a prospective cohort study
Sandooja, Rashi , Saini, Jasmine , Taveras, Elio Ferreira, Gregg-Garcia, Raul, Zhang, Catherine D , Fell, Vanessa , Peersen, Anina, Achenbach, Sara J., Atkinson, Elizabeth J. , Garcia, Raul Gregg , Ferreira Taveras, Elio, Bancos, Irina , Saini, Jasmine , Garcia, Raul G , Gompel, Jamie J. Van , Young, William F. , Bancos, Irina

European Journal of Endocrinology | May 3, 2025 | Volume: 192 | Issue: 5 | Pages: 621-630

10.1093/ejendo/lvaf092 Get It

Abstract Objective Glucocorticoid withdrawal syndrome (GWS) may develop in patients following successful surgery for endogenous hypercortisolism. Effective strategies to minimize GWS and improve quality of life (QoL) are currently lacking. We aimed to determine the impact of hydrocortisone vs prednisone therapy on GWS and QoL during the first 12 weeks postsurgery. Methods Single-center prospective cohort study (2019-2024) of adults with endogenous hypercortisolism who developed postoperative adrenal insufficiency and treated with either prednisone or hydrocortisone. Quality of life was assessed with Short Form-36 (SF-36) and Cushing QoL questionnaires at baseline and at 12 weeks postsurgery. GWS was assessed using weekly AddiQoL questionnaires for the first 12 weeks postsurgery. Results Of 165 patients, 101 (61%) were treated with hydrocortisone and 64 (39%) with prednisone. At baseline, no group differences were found in the hypercortisolism subtype, comorbidities, or QoL assessments. At follow-up, no group differences in final total daily hydrocortisone equivalent dose were seen. When adjusting for the baseline QoL assessment, patients treated with prednisone demonstrated a higher degree of improvement in their QoL, particularly in the SF-36 mental component score (estimate 0.33, 95% CI, 0.04-0.63), SF-36 role-emotional limitation (estimate 0.52, 95% CI, 0.2-0.84), and SF-36 body pain (estimate 0.31, 95% CI, 0.07-0.56) subcomponents. In the multivariable analysis of age, sex, body mass index, glucocorticoid type, baseline clinical severity score, and baseline QoL assessment, prednisone therapy was an independent predictor of better SF-36 mental component at 12 weeks postsurgery. Conclusions Prednisone therapy was associated with better mental health QoL than hydrocortisone at 12 weeks postsurgery in patients with hypercortisolism.
Cognition in patients with mild autonomous cortisol secretion at baseline and post-adrenalectomy
Saini, Jasmine , Nathani, Rohit , Singh, Sumitabh , Ebbehøj, Andreas , Thangamuthu, Karthik, Suresh, Malavika , Zhang, Catherine D , Nevin, S, Fell, Vanessa , Atkinson, Elizabeth J. , Achenbach, Sara J., Nevin, Sophia, Stricker, Nikki H. , Bancos, Irina , Saini, Jasmine , Ebbehøj, Andreas Ladefoged , Bancos, Irina

European Journal of Endocrinology | December 13, 2024 | Volume: 191 | Issue: 6 | Pages: 636-645

10.1093/ejendo/lvae157 Get It

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.
8740 Visceral Adipose Tissue Assessment in Patients With Mild Autonomous Cortisol Secretion Using Dual-Energy X-Ray Absorptiometry: A Cross-Sectional Study
Zhang, Catherine D , Fell, Vanessa , Achenbach, Sara J., Saini, Jasmine , Atkinson, Elizabeth, Bancos, Irina

Journal of the Endocrine Society | October 5, 2024 | Volume: 8 | Issue: Supplement_1 | Pages: No page available

10.1210/jendso/bvae163.321 Get It

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
12444 Steroid Profiling And Circadian Cortisol Secretion In Patients With Mild Autonomous Cortisol Secretion: A Single-Center Cross-Sectional Study
Singh, Sumitabh , Zhang, Catherine D , Nathani, Rohit, Fell, Vanessa , Atkinson, Elizabeth J. , Achenbach, Sara J., Rivard, Ann L, Grebe, Stefan K. , Saini, Jasmine , Ebbehøj, Andreas , Nathani, Rohit , Singh, Ravinder , Bancos, Irina

Journal of the Endocrine Society | October 5, 2024 | Volume: 8 | Issue: Supplement_1 | Pages: No page available

10.1210/jendso/bvae163.295 Get It

Abstract Disclosure: J. Saini: None. S. Singh: None. A.L. Ebbehøj: None. C.D. Zhang: None. R. Nathani: None. V. Fell: None. E. Atkinson: None. S. Achenbach: None. A. Rivard: None. R.J. Singh: None. S.K. Grebe: None. I. Bancos: None. Abstract Context: Mild autonomous cortisol secretion (MACS) is diagnosed based on post-dexamethasone cortisol>1.8 mcg/dL. Scarce evidence exists on steroid circadian secretion and steroid metabolome in MACS. Objective: To characterize 24-hour urine steroid metabolome in patients with MACS and determine circadian differences in urine steroid profiling and cortisol concentrations in patients with MACS versus referent subjects. Design: Cross-sectional study, 2018-2023. Setting: Referral center Participants: 72 patients with MACS and 72 age-, sex-, BMI-, and menopausal status-matched referent subjects. Measurements: Urine was collected over a 24-hour (h) period in separate day- and night-time collections. High-resolution mass spectrometry assay was used to measure 25 steroids. A subgroup of patients and referent subjects were admitted for every 2-hour serum measurement of free and total cortisol. Outcomes: Steroids, sums, and ratios Results: Patients with MACS had lower mcg/24h median androgens (2084 vs 3283, P<0.001), higher glucocorticoids (15754 vs 12936, P<0.001), and higher glucocorticoid/androgen ratio (8.7 vs 3.9, P<0.001). Steroid day/night ratios were lower in patients when compared to referent subjects, reflecting a higher relative nocturnal steroid production in MACS. In a subgroup of 12 patients with MACS and 10 referent subjects, the 24-hour area under the curves for total and free cortisol were similar. However, nocturnal mean total (5.3 vs 4.0 mcg/dL, P=0.056) and free (0.2 vs 0.1 mcg/dL, P=0.035) cortisol were higher in patients vs referent subjects. Conclusion: Patients with MACS demonstrate an abnormal urine steroid metabolome, with a high glucocorticoid to androgen ratio, and a higher nocturnal steroid production. Presentation: 6/3/2024
Steroid Profiling and Circadian Cortisol Secretion in Patients With Mild Autonomous Cortisol Secretion: A Cross-sectional Study
Saini, Jasmine , Singh, Sumitabh , Ebbehøj, Andreas , Zhang, Catherine D , Nathani, Rohit, Fell, Vanessa , Atkinson, Elizabeth J. , Achenbach, Sara J., Rivard, Ann L, Grebe, Stefan K. , Atkinson, Elizabeth , Achenbach, Sara, Rivard, Ann, Grebe, Stefan K G , Bancos, Irina , Saini, Jasmine , Ebbehøj, Andreas Ladefoged , Nathani, Rohit , Singh, Ravinder , Bancos, Irina

The Journal of Clinical Endocrinology & Metabolism | July 9, 2024 | Volume: 110 | Issue: 2 | Pages: 542-553

10.1210/clinem/dgae468 Get It

Abstract Context Mild autonomous cortisol secretion (MACS) is diagnosed based on postdexamethasone cortisol >1.8 µg/dL. Scarce evidence exists on steroid circadian secretion and steroid metabolome in MACS. Objective To characterize 24-hour (h) urine steroid metabolome in patients with MACS and determine circadian differences in urine steroid profiling and cortisol concentrations in patients with MACS vs referent subjects. Methods Cross-sectional study, 2018-2023, at a referral center. Patients with MACS and age-, sex-, body mass index–, and menopausal status–matched referent subjects were included. Urine was collected over a 24 hour period as separate daytime and nighttime collections. High-resolution mass spectrometry assay was used to measure 25 steroids. A subgroup of patients and referent subjects was admitted for serum measurements of free and total cortisol every 2 hours. Outcomes were steroids, steroid sums, and ratios. Results Patients with MACS (n = 72) had lower µg/24 hour median androgens (2084 vs 3283, P < .001), higher glucocorticoids (15 754 vs 12936, P < .001), and higher glucocorticoid/androgen ratio (8.7 vs 3.9, P < .001) than referent subjects. Patients also had lower steroid day/night ratios than referent subjects, reflecting a higher relative nocturnal steroid production in MACS. In a subgroup of 12 patients with MACS and 10 referent subjects, the 24-hour areas under the curve for total and free serum cortisol were similar. However, evening mean total (5.3 vs 4.0 µg/dL, P = .056) and free (0.2 vs 0.1 µg/dL, P = .035) cortisol was higher in patients vs referent subjects. Conclusion Patients with MACS demonstrate an abnormal urine steroid metabolome, with a high glucocorticoid to androgen ratio, and a higher nocturnal steroid production.
Clinical and imaging presentations are associated with function in incidental adrenocortical adenomas: a retrospective cohort study
Hamidi, Oksana , Shah, Muhammad Shahmeer Ullah , Zhang, Catherine D , Lazik, Natalia, Li, Dingfeng , Singh, Sumitabh , Iñiguez‐Ariza, Nicole M. , Raman, Ram, Carafone, Lindsay , Khanna, Aakanksha, Yan, Qi , Natt, Neena, Hartman, Robert P. , McKenzie, Travis J. , Yan, Qi , Bancos, Irina , Hamidi, Oksana , Shah, Muhammad, Hurtado, Maria D. , Young, William F. , Bancos, Irina

European Journal of Endocrinology | June 28, 2024 | Volume: 191 | Issue: 1 | Pages: 47-54

10.1093/ejendo/lvae078 Get It

Abstract Objective The aim of this study is to assess whether clinical and imaging characteristics are associated with the hormonal subtype, growth, and adrenalectomy for incidental adrenal cortical adenomas (ACAs). Design This is a single-center cohort study. Methods Consecutive adult patients with incidental ACA were diagnosed between 2000 and 2016. Results Of the 1516 patients with incidental ACA (median age 59 years, 62% women), 699 (46%) had nonfunctioning adenomas (NFAs), 482 (31%) had mild autonomous cortisol secretion (MACS), 62 (4%) had primary aldosteronism (PA), 39 (3%) had Cushing syndrome, 18 (1%) had PA and MACS, and 226 (15%) had incomplete work-up. Age, sex, tumor size, and tumor laterality, but not unenhanced computed tomography Hounsfield units (HU), were associated with hormonal subtypes. In a multivariable analysis, ≥1 cm growth was associated with younger age (odds ratio [OR] = 0.8 per 5-year increase, P = .0047) and longer imaging follow-up (OR = 1.2 per year, P < .0001). Adrenalectomy was performed in 355 (23%) patients, including 38% of MACS and 15% of NFA. Adrenalectomy for NFA and MACS was more common in younger patients (OR = 0.79 per 5-year increase, P = .002), larger initial tumor size (OR = 2.3 per 1 cm increase, P < .0001), ≥1 cm growth (OR = 15.3, P < .0001), and higher postdexamethasone cortisol (OR = 6.6 for >5 vs <1.8 μg/dL, P = .002). Conclusions Age, sex, tumor size, and laterality were associated with ACA hormonal subtype and can guide diagnosis and management. Tumor growth was more common with younger age and longer follow-up. Unenhanced HU did not predict hormonal subtype or growth. Adrenalectomy for MACS and NFA was mainly performed in younger patients with larger tumor size, growth, and elevated postdexamethasone cortisol.
THU603 Bone Fragility In Mild Autonomous Cortisol Secretion: A Cross-Sectional Cohort Study
Zhang, Catherine D , Singh, Sumitabh , Suresh, Malavika, Thangamuthu, Karthik, Nathani, Rohit, Fell, Vanessa , Achenbach, Sara J., Atkinson, Elizabeth J. , Saini, Jasmine , Nathani, Rohit , Ebbehøj, Andreas , Khosla, Sundeep , Bancos, Irina

Journal of the Endocrine Society | October 5, 2023 | Volume: 7 | Issue: Supplement_1 | Pages: No page available

10.1210/jendso/bvad114.133 Get It

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 >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 <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