Citations

Abstract Disclosure: S.W. Ing: Research Investigator; Self; BridgeBio Pharma. P. Harmatz: Research Investigator; Self; BridgeBio Pharma. S. Mora: Research Investigator; Self; BridgeBio Pharma. E.A. Imel: Research Investigator; Self; BridgeBio Pharma. P.J. Tebben: Research Investigator; Self; BridgeBio Pharma. M.L. Warren: Research Investigator; Self; BridgeBio Pharma, Ascendis, Amolyt. Speaker; Self; Ascendis. N. Ma: Research Investigator; Self; Calcilytix Therapeutics, Ultragenyx, Inozyme. Other; Self; Up To Date. A.A. Khan: Research Investigator; Self; BridgeBio Pharma, Ascendis. A. Palermo: Research Investigator; Self; BridgeBio Pharma. B. Decallonne: Research Investigator; Self; BridgeBio Pharma. S. Lemoine: Research Investigator; Self; BridgeBio Pharma, Kyowa Kirin. G. Mantovani: Research Investigator; Self; BridgeBio Pharma. A. Linglart: Consulting Fee; Self; Alexion, Novo Nordisk, Merck, Pfizer, Inc.. Research Investigator; Self; BridgeBio Pharma, Kyowa Kirin. H. Wasserman: Research Investigator; Self; BridgeBio Pharma. A.P. Barbosa: Research Investigator; Self; BridgeBio Pharma. C. Cardot-bauters: Research Investigator; Self; BridgeBio Pharma. M. Roberts: Employee; Self; BridgeBio Pharma. A. Mathew: Employee; Self; BridgeBio Pharma. S. Adler: Employee; Self; BridgeBio Pharma. M.C. Zillikens: Research Investigator; Self; BridgeBio Pharma. R.J. Clifton-Bligh: Consulting Fee; Self; Ipsen, Kyowa Kirin, Amgen Inc, Eisai. Research Investigator; Self; BridgeBio Pharma. L. Rejnmark: Research Investigator; Self; BridgeBio Pharma, Ascendis, Amolyt, Takeda, Kyowa Kirin. Autosomal dominant hypocalcemia type 1 (ADH1), caused by gain-of-function calcium-sensing receptor gene (CASR) variants, is characterized by low parathyroid hormone (PTH) concentrations, hypocalcemia, hypercalciuria, hyperphosphatemia and hypomagnesemia. While a rare disease, ADH1 is one of the more frequently identified causes of genetic hypoparathyroidism. Conventional therapy includes calcium (Ca) and/or active vitamin D, but this regimen incompletely corrects the hypocalcemia and is associated with persistent hypercalciuria, which may result in renal complications including nephrocalcinosis (NC), nephrolithiasis (NL), and chronic kidney disease (CKD). The CLARIFY disease monitoring study [NCT05227287] is a global, multicenter, longitudinal study to understand disease burden, management, and progression in children and adults with ADH1 over a 5-year period. Here we report data on the characteristics of adult participants at study entry. As of November 2023, 45 adults (≥18 years) with ADH1 were enrolled, with a mean±SD age of 42.1±16.5 years (range 18-80). The mean±SD age of a hypocalcemia diagnosis was 19.1±19.1 years, while the mean±SD age for a diagnosis of ADH1 was 28.2±20.6 years. As reported on medical history, in decreasing order of prevalence, 36% (16) had NC, 22% (10) had intracranial calcifications, 11% (5) had history of seizures, 11% (5) had CKD, 9% (4) had cataracts, 7% (3) had NL, and 4% (2) had undergone renal transplant. Treatment data were available for 43 participants and included the following: 74% (32) Ca and active vitamin D, 9% (4) Ca alone, 9% (4) active vitamin D alone, 37% (16) magnesium, 33% (14) thiazide diuretics, 26% (11) potassium, 7% (3) phosphate binder, 7% (3) PTH, and 5% (2) no treatment. Mean±SD fasting values collected prior to conventional therapy dose are presented. PTH concentrations (10.1±8.2 pg/mL [nl 15-65]) and albumin-corrected calcium ([cCa]=7.5±1.0 mg/dL [nl 8.5-10.5]) were low. Despite the low mean cCa, the mean 24-hr urine calcium was elevated (268±183 mg/d, [nl <250 women, <300 men]). Blood phosphate was 4.8±0.8 mg/dL [nl 2.5-4.8] while blood magnesium was 1.8±0.2 mg/dL [nl 1.8-2.4]. 25-OH vitamin D was 35.0±13.5 ng/mL [nl 30-80]. Renal function as assessed by CKD-EPIcr_R showed eGFR of 86±23 mL/min/1.73m² (range 36-123). This study represents the largest cohort of adults with ADH1 described to date. These data highlight variability in therapeutic approaches in a real-world setting with some participants receiving up to 6 different medications/supplements. Despite being followed in expert centers, and treated with available therapies, patients on average have low cCa with relatively high 24-hr urine calcium excretion. The CLARIFY study provides an opportunity to better understand the progression and burden of disease in participants with ADH1. Presentation: 6/3/2024

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: L. Rahimi: None. F. Al-Khazal: None. N. Becker: None. L. Maher, III: None. Carriers of loss-of-function alleles in genes encoding the four succinate dehydrogenase (SDH) subunits exhibit a heightened risk for pheochromocytoma/paraganglioma (PPGL), a rare neuroendocrine tumor of chromaffin cells. Tumorigenesis begins with the somatic loss of the remaining functional gene copy, resulting in a cell devoid of functional SDH. Compared to wild-type immortalized chromaffin cells (WT imCCs), SDHB-KO immortalized chromaffin cells (SDHB-KO imCCs) are larger, grow more slowly, display deformed mitochondria, show strikingly heightened succinate accumulation, and altered metabolism. Among several mechanisms proposed to link SDH deficiency with PPGL tumorigenesis, the accumulation of succinate as an oncometabolite is a leading hypothesis. We describe two attempts to suppress succinate accumulation in SDHB-KO imCCs. First, riboflavin has previously been shown to enhance residual SDHA flavinylation and enzymatic function, possibly reducing succinate levels by supporting conversion of accumulated succinate to fumarate in the absence of SDHB. We tested this by treating WT and SDHB-KO imCCs with 5 µM riboflavin for 2 weeks. Metabolomic analysis did not show decreased succinate, suggesting that enzyme activity of any remaining SDHA subunit was not rescued by increased flavinylation. Second, we envisioned a gene therapy approach to replace defective SDHB with a rescuing transgene. SDHB-KO imCCs received DNA encoding SDHB or SDHC cDNAs via transposon technology, confirmed by PCR and analyzed by western blot analyses. These studies showed that whereas WT imCCs successfully expressed processed transgene products in mitochondria, SDHB-KO imCCs could not process or transport rescuing SDH subunits into mitochondria. This shows that transposed SDHB-KO imCCs cannot properly express a rescuing SDHB subunit and do not revert to a wild-type phenotype. It is likely that the severely damaged mitochondria of SDHB-KO imCCs are incompetent to process and import rescuing SDHB subunits, so unprocessed protein accumulates without effect. This defect may lie in the mitochondrial targeting peptide recognition system because the targeting peptide of rescuing SDHB protein is not removed in SDHB-KO imCCs as judged by western blotting. In summary, we show the failure of two conceptually simple tactics to suppress succinate accumulation in SDHB-KO imCCs with highly defective mitochondria: rescue of SDHA by supporting flavinylation, or rescue of SDHB with a replacement gene copy. Further research may allow screening for small molecules that suppress succinate accumulation by other mechanisms. It remains to be determined if blocking succinate accumulation would be therapeutic in SDH-loss PPGL tumors. Presentation: 6/1/2024

Abstract Disclosure: J. Yang: None. J. Burrello: None. J. Goi: None. T.A. Williams: None. W.F. Young: Consulting Fee; Self; Arena Pharmaceuticals, Inc.. Other; Self; Crinetics Pharmaceuticals. P.J. Fuller: None. P. Investigators: None. Primary aldosteronism (PA) is the most common endocrine cause of hypertension. Mineralocorticoid receptor antagonists, at adequate doses, lower blood pressure and cardiovascular risk in patients with PA. However, there is a lack of a standardized approach to medical therapy and subsequent outcomes assessment. We aimed to: 1) establish criteria for assessing outcomes of targeted medical treatment of PA, and 2) evaluate outcomes using these criteria across an international cohort. A panel of 31 PA experts from 31 centres across four continents used the Delphi method, including three rounds of online questionnaires, to reach consensus. Clinical data were then collected from consecutive patients with PA who started targeted medical treatment between 2016 and 2021 at the participating centres. Consensus was reached for six outcomes, including complete, partial, or absent biochemical response, and complete, partial, or absent clinical response. “Complete biochemical response” was defined as “correction of hypokalemia without potassium supplementation, and normalization of plasma renin activity or concentration”; while “absent biochemical response” was defined as “persistent hypokalemia and/or persistently suppressed or low plasma renin activity or concentration without change from baseline”. “Complete clinical response” was defined as “normal blood pressure without additional antihypertensive medications”; while “absent clinical response” was defined as “the same or increased blood pressure compared to before targeted treatment with same or more antihypertensive medications, not counting targeted therapy”. Of 1483 patients (mean age 52y, 48% female) from 28 centers, 232 (16%) had a complete clinical response, and 719 (49%) had a complete biochemical response at the most recent follow-up (median 29 months after treatment initiation). Compared to those with partial or absent clinical response, patients with complete clinical response had a significantly higher proportion of women and lower proportion with diabetes, stroke or left ventricular hypertrophy. They also had a significantly shorter duration of hypertension, lower BMI, higher eGFR and lower defined daily dose of antihypertensives at baseline. In contrast, these differences were not observed in those with a complete, partial or absent biochemical response. The defined daily dose of targeted therapy did not differ across the various response categories. In conclusion, we have established an international expert consensus for standardized criteria to evaluate the response to targeted medical treatment of PA, facilitate comparisons of outcome data and guide clinicians who manage PA. In a retrospective international cohort, less than half of medically-treated patients reached the established biochemical treatment targets. Further work is needed to increase the rate of complete response. Presentation: 6/3/2024

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

Abstract Disclosure: M.D. Hurtado: None. E. Tama: None. D. Hodge: None. A. Weston: None. S. Fahad: None. K. Ruddy: None. J. Olson: None. F. Coach: None. R. Carter: None. S. D'Andre: None. A. Acosta: Consulting Fee; Self; Amgen Inc. Grant Recipient; Self; Vivus USA, Novo Nordisk. C. Shufelt: None. Background: Breast cancer (BC) is the most common cancer in women. Weight gain after treatment for early-stage BC is associated with a higher risk of recurrence. Excess adiposity is also a major risk factor for cardiovascular disease, the leading cause of non-BC related death in BC survivors. This study aimed to describe weight trends in a large cohort of BC survivors and to identify predictors of weight gain after BC diagnosis. Methods: This was a retrospective study of BC survivors from the prospectively consented Mayo Clinic Breast Cancer Registry, which has enrolled >10,000 patients seen at least once at Mayo Clinic Rochester for a BC diagnosed within the prior year. We extracted data on weights at baseline, and years 1, 4, and 6 after BC diagnosis to generate longitudinal weight trajectory curves on the change from baseline. Weights were either reported by patients in the registry questionnaires or extracted from the electronic health records. We identified BC survivors with weight gain >10% from baseline weight at years 1, 4, and 6. We then conducted univariable logistic regression analyses to identify predictors of >10% weight gain. Variables considered included: demographics, anthropometrics, BC clinical and pathologic characteristics, BRCA 1 and 2 genetic mutation status, and treatment (surgery, neoadjuvant or adjuvant chemotherapy, and/or radiotherapy). Results: We included 4744 BC survivors, mostly white (95%) and non-Hispanic (91%), with a mean age and weight at BC diagnosis of 58 ± 13 years and 76 ± 18 kg. Most patients had clinical stage I (43%) and ER+ and PR+ BC (83% and 76%, respectively). Most patients underwent breast preserving surgery (62%), half received radiation (54%), one third (36%) received systemic chemotherapy, and two thirds (61%) received endocrine therapy. At one year after BC diagnosis the average weight change was negligible compared to baseline (mean difference -0.2 ± 8 kg), but there were small but significant average increases by years 4 and 6 (0.5 ± 9 kg, p=0.002; and 0.8 ± 10 kg, p<0.001; respectively). At years 1, 4, and 6, the percentage of BC survivors gaining >10% of their baseline weight was 10%, 15%, and 18%, respectively. Baseline characteristics associated with >10% weight gain at 6 years included lower baseline weight (p<0.001), younger age at BC diagnosis (p<0.001), more advanced clinical and pathologic BC stage (p=0.008), ER+ and PR+ tumor biology (p=0.02 for both), BRCA2 mutation (p<0.001), mastectomy (compared to breast preserving surgeries, p=0.008), the use of systemic chemotherapy treatment (p<0.001), and the use of endocrine therapy (p=0.03). Conclusion: While most BC survivors do not experience weight gain after survivorship, 1 out 5 may experience excessive weight gain of more than 10%. Baseline anthropometric and BC-related variables are associated with excessive weight gain and could be used as predictors of weight gain in this population. Presentation: 6/3/2024

Abstract Disclosure: E.R. Uddenberg: None. N. Safwan: None. G. Cook-Wiens: None. O. Obrutu: None. M. Saadedine: None. M.D. Hurtado: None. S. Faubion: None. M.D. Pisarska: None. S.L. Berga: None. J.E. Manson: None. C.N. Bairey Merz: None. C.L. Shufelt: None. Background: Functional hypothalamic amenorrhea (FHA) occurs in women of reproductive age and is a common form of secondary amenorrhea that results in hypoestrogenemia and hypercortisolemia. The underlying cause of FHA is due to a mismatch between energetic intake and expenditure that often manifests as disordered eating, excessive exercise, and psychosocial stress. Previous research identified that 1 in 3 women with FHA had endothelial dysfunction, a preclinical marker for cardiovascular disease. We sought to evaluate the nutrition content in young women with FHA compared to eumenorrheic controls and further assess the relationship to endothelial dysfunction. Methods: We enrolled 30 women with FHA and 29 eumenorrheic controls, not on hormones. FHA was defined as ≥3 consecutive months of amenorrhea, estradiol <50 pg/mL, FSH<10 mIU/L, and LH<10 mIU/L, and exclusion of polycystic ovary syndrome, hyperprolactinemia, thyroid dysfunction, and pregnancy. Eumenorrheic controls had monthly menses with ovulation (progesterone ≥4 ng/mL). Vascular function was measured using EndoPAT 2000 (Itamar® Medical Ltd) to calculate the reactive hyperemic index (RHI). An RHI ≤1.67 indicates endothelial dysfunction. Nutritional intake was collected using a 3-day food diary and analyzed using ESHA Research Food Processor® Nutrition Analysis. Percent (%) recommendation values for nutrition content comparison were calculated based on height, weight, and age. Statistical analysis included Analysis of Variance and Kruskal Wallis test with nonparametric variables reported as median [IQR]. Results: The mean age and BMI of FHA and controls were 26.4 ± 6.2 yrs and 30.3 ± 3.7 yrs (p=0.008), and 21.6 ± 6.2 and 21.8 ± 2.0 kg/m2 (p=0.16), respectively. The median months of FHA amenorrhea was 12 months [5.0, 34.0]. After adjusting for age, there was no difference in caloric intakes in women with FHA compared to controls (1783.9 [1465, 2011] kcal vs. 1731.9 [1578, 1982] kcal, p=0.73); however FHA has higher intake of grams of protein (84.2 [74, 112] g vs. 74 [59, 92] g, p=0.0036), and higher grams of dietary fiber (30.1 [22, 43] g vs. 17.3 [15, 23] g, p=0.0037), respectively. In women with FHA, endothelial dysfunction was associated with a higher % recommended calories (p=0.0098), calories from fat (p=0.02), grams of saturated fat (p=0.03), and grams of carbohydrates (p=0.049). Conclusions: Our results demonstrate that women with FHA consumed similar daily calories, although more grams of protein and dietary fiber than controls. In women with FHA, higher calories, calories from fat, grams of saturated fat and carbohydrates were associated with endothelial dysfunction. Future studies should aim to identify other factors related to endothelial dysfunction among women with FHA and whether some FHA phenotypes are associated with more endothelial dysfunction than others. Presentation: 6/1/2024

Abstract Disclosure: B. Vekony: None. G. Nyiro: None. Z. Herold: None. J. Fekete: None. F. Ceccato: None. S. Gruber: None. L. Kurzinger: None. M. Parasiliti-Caprino: None. B. Szeredas: None. S. Syed Mohammed Nazri: None. V. Fell: None. M. Bassiony: None. E.A. Azizan: None. I. Bancos: None. F. Beuschlein: None. P. Igaz: None. Background: The differentiation of uni- and bilateral forms of primary aldosteronism (PA) is of pivotal clinical relevance. Whereas unilateral PA warrants surgical treatment, bilateral PA is treated by aldosterone antagonists. The most reliable way to differentiate these two entities is adrenal venous sampling (AVS) that is an invasive method with limited availability and requiring great expertise. Aim: To develop a circulating blood-borne microRNA-based approach using machine learning for the differentiation of uni- and bilateral PA. Methods: Circulating microRNA profiling on an Illumina MiSeq platform was performed on total RNA samples isolated from EDTA-anticoagulated blood specimens taken by AVS from 18 pairs of right and left suprarenal veins (10 uni-, 8 bilateral PA). Significantly differentially expressed microRNAs were analyzed by a neural network (90-10% learner-tester cross-validation simulation). From the top 29 significantly differentially expressed microRNAs, 9 were selected for validation by Taqman RT-qPCR on a separate cohort of 30 AVS-confirmed samples (15-15 uni- and bilateral forms) both on plasma samples from adrenal as well as from peripheral veins. The method was finally tested on another independent cohort of peripheral blood samples from 80 patients (40 uni- and 40 bilateral PA). Results: Regarding the 9 microRNAs selected for validation, microRNA abundance was non-significantly lower in peripheral samples compared to AVS samples. By analyzing peripheral plasma samples, ten combinations of 4-8 microRNAs from the pool of 9 microRNAs turned out to have maximal sensitivity and specificity values over 85 %. The best combination included 6 microRNAs with a sensitivity of 86.3 % and a specificity of 87.91 % (AUC = 0.871). The inclusion of further parameters such as imaging, potassium and renin levels did not improve the model’s performance. Conclusion: The analysis of circulating blood-borne microRNAs represents a minimally invasive and potentially reliable way of differentiating uni- and bilateral PA. If bilateral PA is confirmed by the model, no more localization efforts would be necessary thus simplifying the management of PA patients. This would be relevant both from the patient’s and a public health perspective. Presentation: 6/3/2024

Abstract Disclosure: B. Vekony: None. G. Nyiro: None. Z. Herold: None. J. Fekete: None. F. Ceccato: None. S. Gruber: None. L. Kurzinger: None. M. Parasiliti-Caprino: None. B. Szeredas: None. S.K. Nazri: None. V. Fell: None. M. Bassiony: None. E.A. Azizan: None. I. Bancos: None. F. Beuschlein: None. P. Igaz: None. Background: The differentiation of uni- and bilateral forms of primary aldosteronism (PA) is of pivotal clinical relevance. Whereas unilateral PA warrants surgical treatment, bilateral PA is treated by aldosterone antagonists. The most reliable way to differentiate these two entities is adrenal venous sampling (AVS) that is an invasive method with limited availability and requiring great expertise. Aim: To develop a circulating blood-borne microRNA-based approach using machine learning for the differentiation of uni- and bilateral PA. Methods: Circulating microRNA profiling on an Illumina MiSeq platform was performed on total RNA samples isolated from EDTA-anticoagulated blood specimens taken by AVS from 18 pairs of right and left suprarenal veins (10 uni-, 8 bilateral PA). Significantly differentially expressed microRNAs were analyzed by a neural network (90-10% learner-tester cross-validation simulation). From the top 29 significantly differentially expressed microRNAs, 9 were selected for validation by Taqman RT-qPCR on a separate cohort of 30 AVS-confirmed samples (15-15 uni- and bilateral forms) both on plasma samples from adrenal as well as from peripheral veins. The method was finally tested on another independent cohort of peripheral blood samples from 80 patients (40 uni- and 40 bilateral PA). Results: Regarding the 9 microRNAs selected for validation, microRNA abundance was non-significantly lower in peripheral samples compared to AVS samples. By analyzing peripheral plasma samples, ten combinations of 4-8 microRNAs from the pool of 9 microRNAs turned out to have maximal sensitivity and specificity values over 85 %. The best combination included 6 microRNAs with a sensitivity of 86.3 % and a specificity of 87.91 % (AUC = 0.871). The inclusion of further parameters such as imaging, potassium and renin levels did not improve the model’s performance. Conclusion: The analysis of circulating blood-borne microRNAs represents a minimally invasive and potentially reliable way of differentiating uni- and bilateral PA. If bilateral PA is confirmed by the model, no more localization efforts would be necessary thus simplifying the management of PA patients. This would be relevant both from the patient’s and a public health perspective. Presentation: 6/3/2024

Abstract Disclosure: K. Yu: None. S. Athimulam: None. J. Saini: None. R. Kaur: None. R.J. Singh: None. S.K. Grebe: None. Q. Xue: None. I. Bancos: Advisory Board Member; Self; AstraZeneca, Corcept, Novo Nordisk, HRA Pharmaceuticals, Neurocrine, Diurnal, Recordati, Sparrow, Xeris, Spruce, Adrenas. Research Investigator; Self; HRA Pharmaceuticals, Recordati. Context: Early diagnosis is essential to assure a better prognosis in patients with adrenocortical carcinoma (ACC). Guidelines suggested performing urine steroid profiling in patients with indeterminate adrenal tumors to make a noninvasive diagnosis of ACC. However, urine steroid profiling is not widely available. Accuracy of clinically available serum steroids in diagnosing ACC has not been established. Objective: To determine the accuracy of 11-deoxycortisol, 17OH-progesterone, and 17OH-pregnenolone in diagnosing ACC. Design: Prospective single-center cohort study. Participants: Between 2015 and 2023, consecutive patients with adrenal mass were prospectively enrolled in the prospective registry and biobank study. Patients who agreed to contribute a fasting serum sample were included in the study. Exclusion criteria were congenital adrenal hyperplasia, exogenous glucocorticoid use, absence of unenhanced Hounsfield unit measurements (HU), and lack of established reference standard (histopathology, imaging characteristics, 2-year imaging follow up, or 5-year clinical follow up). Measures and Outcomes: measurements included 11-deoxycortisol, 17OH-progesterone, and 17OH-pregnenolone by liquid chromatography–mass spectrometry. Localized Generalized Matrix Learning Vector Quantization (LGMLVQ) analysis was used to develop serum steroid score and assessed with area under receiver operating curve (AUROC). Results: Of 263 patients with adrenal masses, 44 (17%) were diagnosed with ACC, 161 (61%) with adrenocortical adenomas (ACAs), 27 (10%) with other adrenal malignancies, and 31 (12%) with other. HU ≥ 20 were demonstrated in all ACCs, in all but one other adrenal malignancy, and only in 58 (31%) ACAs. All 3 steroids were higher in patients with ACCs vs nonACCs, including when comparing ACCs with functioning ACAs, and with ACAs with HU ≥ 20 (P<0.0001 for all). LGMLVQ analysis yielded a serum steroid score that discriminated between ACC and non-ACC groups with a mean threshold fixed AUROC of 0.823. Serum steroid score of 0.29 demonstrated a mean false negative rate of 0% and a score of 0.61 demonstrated a mean false positive rate of 0%. Conclusions: We showed that measurements of 11-deoxycortisol, 17OH-progesterone, and 17OH-pregnenolone could be valuable in diagnosing ACC. After appropriate validation, serum steroid score could be integrated in clinical practice. Presentation: 6/2/2024