Predicting the outcome of short Synacthen test based on baseline cortisol levels: A single-centered retrospective cohort study at a tertiary care hospital in Sri Lanka.

Short Synacthen test (SST) involves measuring the baseline, 30-, and 60-minute serum cortisol levels, after injecting 250 μg of synthetic adrenocorticotropic hormone or Synacthen (ACTH). This study aimed to review the current clinical practice of performing SST to establish a standardized test protocol and to additionally test the hypothesis regarding performing the 60-minute cortisol test alone and the dependence of overall SST result on baseline cortisol level.Patients >14 years who underwent SST from January 2010 to December 2017 were included. Pearson's chi-square cross-tabulation was used to identify individuals with inconsistent 30- and 60-minute serum cortisol test results. Logistic regression analysis was performed to predict normal responses based on the baseline cortisol value.Of the 965 patients identified from pharmacy, medical, and laboratory records, 849 were included. Mean baseline, 30-, and 60-minute cortisol levels after ACTH injection were 394 ± 286.58, 722 ± 327.11, and 827 ± 369.30 nmol/L, respectively. Overall, 715 (84%) and 134 (16%) patients had normal and abnormal responses, respectively. Primary and secondary adrenal insufficiency was diagnosed in 10% and 35%, respectively, while ACTH levels were not measured in 55% of the patients. Overall, 9.49% (n = 72) of the patients had a suboptimal response at 30 minutes, but reached the threshold value of 550 nmol/L at 60 minutes. This particular subgroup's mean change (240 nmol/L) in cortisol level from baseline to 30-minute was higher than that observed in patients with abnormal response at both time-points (mean change, 152 nmol/L). No patient with 30-minute optimal responses had 60-minute suboptimal responses. The baseline serum cortisol threshold of ≥226 nmol/L had 80% sensitivity, 71% specificity, and 93% positive predictive value for detecting a normal SST (P-value < .0001).Relying on a 60-minute cortisol level can identify all normal and abnormal responses, while relying on 30-minute cortisol level alone may produce false-positives. Additionally, a baseline cortisol level of ≥226 nmol/L is a reliable threshold for determining adequate adrenal function, particularly with a low pretest hypoadrenalism probability.

A Pragmatic Approach to Monitor for Adrenal Axis Recovery After a Failed Short Synacthen Test.

BACKGROUND: Remission of Cushing’s syndrome (CS) is generally defined as morning serum cortisol values <5mcg/dL (<138 nmol/L) or Urine Free Cortisol <10-20ug/dL (< 28 – 56 nmol/d) after tumor resection, which reflects suppression of the hypothalamic-pituitary-adrenal (HPA) axis by sustained hypercortisolism. Endocrine Society guidelines recommend glucocorticoid replacement until the HPA axis is normal as assessed by a morning (AM) or post-ACTH stimulation test cortisol level of approximately 18 ug/dL (500 nmol/L) or greater (1). Patients with subnormal cortisol levels remain on glucocorticoid until retested in 3-6 months. The goal of this study was to determine whether a baseline cortisol value predicts a normal response to the ACTH stimulation test.Methods: We reviewed 235 ACTH stimulation (stim) tests conducted on 76 patients with secondary adrenal insufficiency following remission of CS. Patients had resection of a single adrenal gland (n=7), pituitary adenoma [with (n=3) or without (n = 47) subsequent radiation], 70% of pituitary tissue (n=5), or ACTH secreting intrathoracic tumor (n=13). One had an ectopic ACTH secreting tumor in spontaneous remission (n=1). ACTH stim tests were conducted between 0800h and 0900h, 24 hours after the last dose of glucocorticoid, using 250 mcg of cosyntropin intravenously. Cortisol levels were measured just before administration of cosyntropin, and 30 and 60 minutes afterwards. Patients were considered to have passed the test if baseline or peak cortisol values reached > 18mcg/dL. Baseline cortisol values were compared to the ‘pass’ rate.Results: Baseline F values (ug/dL) and passing rates (# pass/total) were:<4: 1/91;4-4.9: 2/27;5-5.9: 8/31;6-6.9: 2/21;7-7.9: 7/25;8-8.9: 4/12;9-9.9: 8/12;>10 - < 15: 6/1115 – 19.5: 5/5Thus, Am cortisol values >9 ug/dl were significantly more likely to predict a normal response to ACTH stim than lower values (p<0.0001). ACTH values (n=184) did not predict peak F levels. However, no patient with ACTH value <5 pg/ml passed the test; all had peak F values of 0-10.5.Conclusion: Baseline cortisol can be a guide as to whether the more costly stimulation test is needed. In the small cohort with baseline 0800h – 0900h cortisol >15 ug/dL, all passed the test, suggesting that it is not needed in such patients. We recommend use of an ACTH stimulation test to assess recovery of the HPA axis when a morning cortisol reaches 9 mcg/dL, with an expected pass rate of about 66%.Reference: 1. Nieman LK, Biller BM, Findling JW, Murad MH, Newell-Price J, Savage MO et al. Treatment of Cushing’s Syndrome: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 100:2807, 2015.

Disclosure: N.R. Lawrence: None. B.G. Keevil: None. C. Elder: None. J. Fearnside: None. S. Caunt: None. S. Dixon: None. J.D. Newell-Price: Consulting Fee; Self; Diurnal, Recordati, Crinetics, HRA Pharma. R.J. Ross: Employee; Self; Diurnal. M. Debono: None. Background: The ACTH (Cosyntropin) stimulation test (AST) is the reference standard for diagnosis of adrenal insufficiency. We have demonstrated recently that home waking salivary cortisone accurately predicts the ACTH stimulation test outcome and confirms or excludes adrenal insufficiency in 70% of high-risk patients (in press: Home Waking Salivary Cortisone to Screen for Adrenal Insufficiency NEJM Evidence). 11-hydroxyandrostenedione (11-OHA4) is a weak adrenal androgen whose synthesis is dependent on CYP11B1. Since ACTH drives steroidogenesis, and adrenal androgens are low in patients with adrenal insufficiency, we hypothesised that waking 11-OHA4 could also predict adrenal status. Methods: A prospective, diagnostic accuracy study of waking salivary cortisone was performed in 173 patients at high risk of AI. All patients collected a salivary sample on waking, and then attended the endocrine clinic for an AST with the 30-minute cortisol used to diagnose AI. Salivary cortisone and 11-OHA4 was measured in the waking salivary sample. Biomarker discrimination was assessed by calculation of area under the curve (AUC) of the receiver operator characteristics (ROC) plot. Equivocal results were defined to maintain a sensitivity of 95% and specificity of 95%, and percentage of AST saved by calculating the number of AST needed if used only in equivocal cases. Results: The median (IQR) for 11-OHA4 for patients with AI and no AI was 55 (45 to 110) pmol/l vs 508 (255 to 765) pmol/l; p&amp;lt;0.0001. Salivary 11-OHA4 on waking was highly predictive of adrenal insufficiency (R2=0.63, ROC AUC 0.94), similar to waking salivary cortisone alone (R2=0.65, AUC 0.94). Waking 11-OHA4 performed better than either serum cortisol (R2=0.65, AUC 0.88) or salivary cortisone (R2=0.74, AUC 0.93) collected at the baseline of the AST. Combining both waking salivary 11-OHA4 with waking salivary cortisone further improved discrimination (R2=0.70, AUC 0.96), and using this combination would mean that 78% of ACTH-stimulation tests could be avoided. Conclusion: Waking salivary 11-OHA4 can accurately predict AI with similar discriminatory value as waking salivary cortisone. Combining waking 11-OHA4 with waking salivary cortisone improves discrimination for adrenal insufficiency, is a simple non-invasive test that can be used widely in clinical practice in the ambulatory setting, and obviates the need for AST in 78% of cases with greater patient convenience and lower costs. Presentation: Sunday, June 18, 2023

Corticosteroids are known to cause adrenal suppression. The aim of this study was to assess clinical factors affecting responses to a low dose short synacthen test (LDSST) in asthmatic children using corticosteroids. Patients were recruited from secondary care paediatric asthma populations within the UK. Asthmatic children (5-18 years), receiving corticosteroids, underwent a LDSST (n = 525). Demographics and corticosteroid doses were tested for association with baseline and peak (stimulated) cortisol concentrations. Baseline cortisol was significantly associated with age (log baseline increased 0·04 nm per year of age, P < 0·0001), but not with gender or corticosteroid dose. Peak cortisol was significantly associated with total corticosteroid cumulative dose (decreased 0·73 nm per 200 mcg/day, P < 0·001) but not with age, gender inhaled/intranasal corticosteroid cumulative dose or number of courses of rescue corticosteroids. Biochemically impaired response (peak cortisol ≤500 nm) occurred in 37·0% (161/435) overall, including children using GINA low (200-500 mcg/day beclomethasone-CFC equivalent 32%, n = 60), medium (501-1000 mcg/day (33%, n = 57) and high (>1000 mcg/day 40%, n = 13) doses of inhaled corticosteroid (ICS) similarly, and 36·6% of those using fluticasone ICS ≥500 mcg/day (71/194). Impaired response was more frequent in patients on regular oral corticosteroids (66%, n = 27, P < 0·001). Children with asthma can develop biochemical adrenal suppression at similar frequencies for all ICS preparations and doses. The clinical consequence of biochemical suppression needs further study.

Background Short ACTH stimulation (Synacthen) tests are performed to investigate for adrenal insufficiency. Previous work suggests that morning cortisol concentrations can be used to rule in or out adrenal insufficiency to avoid performance of a Synacthen test. This study aimed to determine the optimal cortisol concentration for rule-in or rule-out adrenal insufficiency based on 30-minute cortisol (COR30) for adequate response using the assay-specific cut-off from The Endocrine Society of Australia/The Australasian Association for Clinical Biochemistry and Laboratory Medicine/The Royal College of Pathologists of Australasia (ESA/AACB/RCPA) Harmonization of Endocrine Dynamic Testing - Adult (HEDTA), in an Asian population. Methods Synacthen tests performed at our institution from 2012-2024, with a baseline cortisol between 6 and 10 am (COR0(6-10)), were extracted from the laboratory database. Plasma cortisol concentrations were measured by Beckman Coulter DxI 800. Synacthen tests were classified as adequate or inadequate based on the Beckman Coulter specific HEDTA cut-off for COR30 of 420 nmol/L. Performance characteristics (sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under receiver operator characteristic (AUROC) curve) of COR0(6-10) concentrations to predict adequate or inadequate response were calculated using Microsoft Excel. Results 4609 Synacthen tests were included, 77% of which had adequate Synacthen response. COR0(6-10) &amp;gt;300 nmol/L could exclude inadequate COR30 response with sensitivity 95%, specificity 48%, PPV 35%, NPV 97%; and COR0(6-10) &amp;gt;364 nmol/L had sensitivity 99%, specificity 29%, PPV 29%, NPV 99%. COR0(6-10) &amp;lt;155 nmol/L could rule-in inadequate COR30 response with sensitivity 53%, specificity 95%, PPV 76%, NPV 87%; and COR0(6-10) &amp;lt;97 nmol/L had sensitivity 35%, specificity 99%, PPV 91%, NPV 84%. AUROC of COR0(6-10) for adequate COR30 response was 0.86. If patients with COR0(6-10) &amp;lt;97 nmol/L and &amp;gt;300 nmol/L did not proceed to Synacthen testing, up to 46% of tests could be avoided, while keeping misclassification under 5%. Conclusions Morning cortisol cut-offs were determined for rule-in and rule-out of adrenal insufficiency in an Asian population. Patients with morning cortisol &amp;gt;300 nmol/L or &amp;lt;97 nmol/L may be able to avoid Synacthen testing unless there is a strong suspicion of clinical discordance. Such a testing strategy could significantly decrease the number of Synacthen tests while keeping misclassification to a minimum.

BackgroundLong-term glucocorticoid (GC) therapy is commonly used to treat rheumatological conditions. This may result in tertiary adrenal insufficiency, as a result of suppression of the HPA axis, when GC doses are weaned/withdrawn. There is little published data about tertiary adrenal insufficiency in this group. This study aims to further evaluate prevalence, characteristics and recovery of adrenal insufficiency in these patients at a large UK teaching hospital.MethodsWe retrospectively identified patients seen in outpatient clinics between January 2014 and September 2019 who had received tapering doses of long-term GC to treat their underlying condition (largely patients with polymyalgia rheumatica, giant cell arteritis or other vasculitis) and had either had a 9am cortisol or short synacthen test (SST). Data were collected using a standardised proforma.ResultsThere was a total of 238 patients, median age of 71 years with a female preponderance (75%). Mean duration of glucocorticoid use was 63.3 months. Mean peak dose of glucocorticoid was 29.2mg.142 patients had 9am cortisol as the first line test to assess adrenal function. 65% of these were considered sub-optimal based on local protocol (cortisol <350nmol/L). 38% of these patients went on to have SST, of which 56% continued to show evidence of sub-optimal cortisol production. All patients where baseline 9am cortisol was <100nmol/L failed to reach stimulated cortisol of >500nmol/L on SST, whereas 31% failed SST if 9am cortisol was 250-350 nmol/L.In total 138 SSTs were performed of which 51% (n=70) were abnormal (cortisol <500nmol/L post synacthen). When baseline cortisol was <100nmol/L on SST, all patients had a suboptimal peak response. However, where baseline cortisol on SST was >350 nmol/L only 3% had a sub-optimal peak cortisol.32 of these patients with an abnormal baseline SST went on to have a repeat SST within 2 years. 50% (n=16) continued to be suboptimal. Of the 32 patients, 38% (n=12) were switched to hydrocortisone with 33% showing complete adrenal recovery, average time to recovery of 25 months. 62% (n=20) patients did not switch, with 60% demonstrating recovery within the same time period (p=0.05). Mean ACTH levels in patients who had sub-optimal SST were 23.1 ng/L (n=19). ACTH levels were not different between those who recovered and those who did not (p=0.23).ConclusionOur study suggests that tertiary adrenal insufficiency is highly prevalent in this cohort of patients with rheumatological conditions requiring long-term glucocorticoid therapy. A 9am cortisol threshold of greater than 350nmol/L excludes most patients with adrenal insufficiency. These data also suggest no significant difference in adrenal recovery if switched to hydrocortisone versus continuing on prednisolone. ACTH levels were not fully suppressed in patients with adrenal insufficiency and did not predict recovery.

Investigating the Clinical Appropriateness of Short Synacthen Testing and Utility of Pretest Cortisol to Predict Short Synacthen Testing Outcomes: A Tertiary Center Experience in Southeast Asia

Background/Aim: To evaluate the association between the cortisol levels and clinical outcomes in preterm infants. Methods: Baseline adrenocorticotropic hormone (ACTH) and cortisol levels and ACTH-stimulated cortisol concentrations after low-dose synthetic ACTH (Synacthen®, 1 µg/kg) were measured in preterm infants <37 weeks of gestational age between the 5th and 7th days of life. Associations between cortisol concentrations and clinical outcomes were examined. The prevalence and prognostic utility of relative adrenal insufficiency (AI) were assessed. Results: Ninety-eight preterm infants were enrolled. Median baseline cortisol and ACTH levels were 13.7 µg/dl (25th-75th percentile, 9.7-21.1 µg/dl) and 11.5 pg/ml (25th-75th percentile, 6.9-22.6 pg/ml), respectively. Median peak cortisol level after ACTH stimulation was 33.6 µg/dl (25th-75th percentile, 27.2-40.2 µg/dl). The prevalence of relative AI, defined as baseline cortisol <15 µg/dl or Δ-cortisol <9 µg/dl, was 65%. Cortisol levels at baseline and at all time points during the test and relative AI were not associated with mortality or any other clinical outcomes. Conclusion: Neither baseline nor ACTH-stimulated cortisol levels were associated with clinical outcomes in preterm infants. A significant proportion of preterm infants hospitalized in the neonatal unit fulfilled the criteria for relative AI; however, relative AI did not affect outcome.

Disclosure: O. Hamidi: Advisory Board Member; Self; Corcept, Neurocrine Biosciences, Amryt Pharma, Recordati Rare Diseases, Lantheus, Xeris. B.H. Salama: None. P. Dogra: None. A.P. Dackiw: None. F. Nwariaku: None. A. Islam: None. A. Mehta: None. S.C. Oltmann: None. S. Mirfakhraee: None. T. McKenzie: None. T.R. Foster: None. M. Lyden: None. B.M. Dy: None. I. Bancos: None. Introduction: Patients with mild autonomous cortisol secretion (MACS) are at risk for adrenal insufficiency (AI) after unilateral adrenalectomy. We aimed to determine the prevalence, predictors, and duration of AI after unilateral adrenalectomy for MACS, and to compare baseline and peak cortisol post cosyntropin stimulation test (CST) in diagnosing AI. Methods: We conducted a dual-center retrospective cohort study of patients with MACS who underwent unilateral adrenalectomy and were evaluated with postoperative cosyntropin stimulation test (CST). AI was diagnosed when postoperative morning cortisol was &amp;lt;10μg/dL and/or CST peak cortisol was &amp;lt;18μg/dL. Baseline and CST peak cortisol levels were considered concordant when both met corresponding cut-offs. Biochemical (BSS) and clinical (CSS) severity scores for hypercortisolism were calculated. Results: In 100 adults with MACS (77% women, median age 56 years, interquartile range [IQR] 48-63), median adenoma size was 2.8 cm (IQR, 2.2-3.7), and 25 (25%) had bilateral nodules. Median BSS was 3 (IQR, 2-5) and median CSS was 4 (IQR, 2-8). After adrenalectomy, AI was diagnosed in 56 (56%) patients. AI was associated with higher BSS, larger tumor size, but not age, sex, BMI, tumor laterality. Baseline and CST peak cortisol levels were concordant in 76% of cases. In 14% of cases morning cortisol was &amp;lt;10μg/dL but CST peak cortisol was ≥18μg/dL, and in 10% of cases morning cortisol was ≥10μg/dL, but CST peak cortisol was &amp;lt;18μg/dL. On a multivariable analysis that included age, sex, BMI, BSS, laterality, and tumor size, only higher BSS (odd ratio [OR] = 1.6 per 1 point) was associated with postoperative baseline cortisol &amp;lt;10μg/dL (P&amp;lt;0.05 for all). Independent predictors of CST peak cortisol &amp;lt;18μg/dL were BSS (OR 1.5 per 1 point) and unilateral adenoma (OR 3.7). During a median postoperative follow up of 13 months, 33 (59%) patients recovered from AI. Median time to recovery was 6.0 months, with AI recovery in 28% of patients by 2 months, 42% by 3 months, 53% by 6 months, and 64% by 12 months. Conclusions: Prevalence of postoperative AI in MACS was 56%. Only 76% of patients had concordant baseline and CST peak cortisol, with peak CST cortisol being more commonly abnormal in patients treated for unilateral MACS. Patients with larger adenomas and higher BSS were at higher risk for AI. Patients with MACS should be counseled about the risk and duration of AI after adrenalectomy. Presentation: 6/3/2024

Background and Objectives: Adrenal insufficiency (AI) is an endocrine disorder characterized by inadequate cortisol production, leading to non-specific symptoms that delay diagnosis. The Low Dose Synacthen Test (LDST) is commonly used to evaluate adrenal function, but traditional cortisol cut-offs may not accurately reflect adrenal function in all patients. This study aims to identify baseline cortisol cut-offs to accurately rule in and out AI, reassess the value of cortisol increment during LDST, and evaluate the accuracy of 30 and 60 min cortisol measurements in diagnosing AI. Materials and Methods: We conducted a cross-sectional analysis of patients who underwent LDST at Farhat Hached University Hospital. Diagnostic accuracy of baseline cortisol levels and cortisol increment was assessed using ROC curve analysis to determine optimal cut-offs for predicting LDST outcomes. Results: Among 163 patients (mean age 42.9 years, 63% female), baseline cortisol ≤ 5.35 μg/dL had 100% specificity but 41.5% sensitivity for LDST failure. Conversely, baseline cortisol ≥ 12.4 μg/dL had 100% sensitivity with 45.9% specificity. Single measurements at 30 and 60 min correctly classified 92.64% and 93.87% of cases, respectively. ROC analysis of 30 and 60 min cortisol increments showed high diagnostic accuracy (AUC 0.923 and 0.914, respectively). The optimal cortisol increment cut-off was 6.35 μg/dL for ruling in AI (99% specificity). Conclusions: We propose a novel AI diagnostic algorithm based on a single 30 min cortisol measurement, complemented by revised baseline cortisol cut-offs and cortisol increment as additional criteria. This approach may enhance diagnostic accuracy and minimize unnecessary testing, warranting further clinical validation.

The short synacthen test (SST), first introduced by Wood et al. 1 in 1965, is widely used to confirm the diagnosis of primary adrenal insufficiency. The optimum method for the diagnosis of secondary adrenal insufficiency remains controversial. The insulin tolerance test (ITT) is accepted by most endocrinologists as the gold standard 2 for the assessment of the hypothalamic-pituitary-adrenal (HPA) axis, but is hazardous at times, with some morbidity and occasional mortality. The short synacthen test is gaining popularity, and by 1994, up to 50% of UK endocrinologists were using it to assess the HPA axis. 3 We describe two cases presenting with hyponatremia in whom hypoadrenalism was suspected, but with normal SST. The secondary adrenal insufficiency was later confirmed in these cases on clinical features, associated hormonal deficiencies, ancillary investigations and most important of all, the therapeutic response to replacement steroids. Case 1 A 63-year-old male presented with a history of six to seven episodes of fainting/loss of consciousness over the previous year-and-a-half. These episodes were never preceded by any palpitations or associated with seizure activity and/or incontinence of urine or feces. He also experienced occasional nausea with vomiting. He was labelled to have ischemic heart disease on the basis of ECG changes, but did not have angina and was taking diltiazem, moduretic (amiloride and hydrochlorothiazide), ranitidine and amitriptyline regularly. He appeared unwell upon admission, and was pale-looking, with a pulse of 90/min. His blood pressure was in the range of 120-140 mm Hg systolic and 70 mm Hg diastolic, but with a significant postural drop of 20 mm Hg. The rest of the examination was unremarkable. Routine investigations revealed serum sodium of 112 mmol/L, potassium of 3.3 mmol/L, and creatinine of 1.0 mg/dL. It was thought that electrolyte imbalance was due to diuretics and associated vomiting. He was rehydrated with normal saline and the

Diagnosing adrenal insufficiency (AI) often requires complex testing, which can be time-consuming and expensive. Dehydroepiandrosterone sulfate (DHEAS) is a promising marker of hypothalamic-pituitary-adrenal axis function; however, its diagnostic performance has not yet been evaluated in a large-scale study. Evaluate the performance of DHEAS and baseline cortisol in assessing AI. Single-center retrospective cohort study. Referral center. Adults who underwent cosyntropin stimulation testing (CST) between 2005 and 2023 and had DHEAS measured within 3 months prior to CST. Area under receiver operating characteristic curve (AUROC) for DHEAS and baseline cortisol. Prevalence of AI based on various DHEAS and baseline cortisol concentrations. Among 1135 patients, 195 (17.2%) had AI. Both baseline cortisol and DHEAS independently had good diagnostic performance with AUROC 0.81 [95% confidence interval (CI) 0.77-0.84 and 0.81 (95% CI 0.78-0.85)], respectively. Time of CST performance had no significant effect on diagnostic accuracy of baseline cortisol while recent glucocorticoid use decreased diagnostic performance of DHEAS (AUROC 0.72 vs 0.83). Only 1.2% of patients with baseline cortisol ≥10 mcg/dL had AI based on CST. Among patients with baseline cortisol between 5 and 9.9 mcg/dL, only 1.3% had AI if DHEAS was ≥60 mcg/dL. Conversely, the majority (72.2%) of patients with both baseline cortisol <5 mcg/dL and DHEAS <25 mcg/dL were found to have AI. DHEAS has good diagnostic performance in assessing AI. Measuring both baseline cortisol and DHEAS concentrations may eliminate the need for further dynamic testing in many patients.

Adrenal Response in Severe Community-Acquired Pneumonia: Impact on Outcomes and Disease Severity

To compare the diagnostic value of adrenocorticotropic hormone (ACTH) stimulation test (AST) with different doses of ACTH combined with midnight administration of 1 mg dexamethasone for the determination of the subtypes of primary hyperaldosteronism (PA). This is a prospective observational study. Patients diagnosed with PA in the Department of Endocrinology, the First Medical Center of of Chinese PLA General Hospital from January 1, 2020 to September 30, 2022 underwent AST with different doses of ACTH. All patients received 1 mg dexamethasone at midnight for inhibition. Then, the patients were randomly assigned to 25-unit and 50-unit ACTH treatment groups by a ratio of 1:2. Subtype classification and diagnosis of aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism (IHA) was made on the basis of adrenal venous blood samples and/or postoperative pathology and clinical follow-up findings. Receiver operating characteristics (ROC) curves were plotted to examine the diagnostic efficacy and the difference of AST by varying doses of ACTH in distinguishing APA and IHA. A total of 82 patients, including 49 patients with APA (59.8%) and 33 patients with IHA (40.2%), were enrolled. There were 29 patients in the 25-unit ACTH group (35.4%) and 53 patients in the 50-unit ACTH group (64.6%). There were no significant differences in age, sex, blood pressure, minimum serum potassium, and biochemical parameters between the 25-unit and 50-unit groups. After ACTH stimulation, plasma aldosterone concentration (PAC), cortisol (F), and PAC/F at different points of time showed no statistical difference between the two groups (P>0.05). The area under the curve (AUC) of PAC in the 25-unit group was higher than that of PAC/F. The AUC of PAC reached the maximum at 90 minutes (0.948, 95% confidence interval [CI]: 0870-1.000) and the optimal cutoff was 38.0 ng/dL, which had a sensitivity of 92.9% and a specificity of 86.7% for differentiating APA and IHA. Similar to the 25-unit group, the maximum AUC of PAC in the 50-unit group was greater than that of PAC/F. The AUC of PAC reached the maximum 90 minutes (0.930, 95% CI: 0.840-0.994) and the optimal cutoff was 39.6 ng/dL, which had a sensitivity of 91.2% and a specificity of 83.3%. The AUC of PAC at different points of time in the 25-unit ACTH group (0.862-0.948) was greater than that of 50-unit ACTH group (0.823-0.930), but the difference was not statistical significance. AST with 25-unit or 50-unit ACTH combined with small-dose dexamethasone can be used in PA subtype determination, ie, differentiation between APA and IHA. The optimal PAC cut-off values for 25-unit or 50-unit ACTH are similar, being 38.0 ng/dL and 39.6 ng/dL, respectively, and both cutoff values show higher sensitivity and specificity at 90 min. The AST with 25-unit ACTH has the smaller dose and the better safety. Therefore, it is recommended for the diagnosis of PA subtypes.