Assay-Specific Spurious ACTH Results Lead to Misdiagnosis, Unnecessary Testing, and Surgical Misadventure-A Case Series

Adrenocorticotropic Hormone Measured by Immulite 1000 and Elecsys Assay Platforms in Suspected Cases of Hypocortisolism: A Word of Caution

OBJECTIVE

Several reports suggested that adrenocorticotropic hormone (ACTH) level measured by Immulite 1000 may be falsely elevated leading to misdiagnosis of etiology of Cushing syndrome. However, when it comes to fallacies of ACTH measurement in suspected cases of hypocortisolism, evidence is limited. We explored the performance of ACTH assays using Immulite 1000 and Elecsys Cobas immunoassay platforms in subjects with hypocortisolism.

METHODS

In this observational, cross-sectional study, 104 patients with haemoglobin E/beta-thalassemia were subjected to 9 am serum cortisol, direct renin concentration, and plasma aldosterone. Plasma ACTH was measured in Immulite 1000 and Elecsys Cobas platforms. Both 1 μg and 250 μg Synacthen stimulation tests were performed to diagnose adrenal insufficiency.

RESULTS

Among 104 patients with haemoglobin E/beta-thalassemia, 34 had primary adrenal insufficiency, 9 had secondary adrenal insufficiency, and 33 had subclinical adrenal insufficiency. Mean plasma ACTH (n = 104) measured by Immulite 1000 and Elecsys was 83.42 ± 63.46 pg/mL versus 52.10 ± 38.14 pg/mL, respectively (P < .001). The values had good correlation (r = 0.341, P < .001); however, the agreement between measured values was not strong (Cohen's κ = 0.208, P = .001). With regard to the diagnosis of primary adrenal insufficiency, specificity of Immulite 1000 was low compared with Elecsys (27.86% vs 80.32%). Furthermore, 2 patients with secondary adrenal insufficiency had inappropriately elevated ACTH measured at Immulite 1000 assay platform.

CONCLUSION

Use of Immulite 1000 platform may result in falsely elevated ACTH values. Physicians should exercise caution while interpreting the results and repeat test using a different assay platform may be considered.

Understanding negative feedback: Changes in high-molecular-weight adrenocorticotropic hormone in adrenocorticotropic hormone-independent Cushing's syndrome

Cushing's syndrome is characterized by chronic glucocorticoid oversecretion and diverse clinical manifestations. Distinguishing between adrenocorticotropic hormone (ACTH)-independent and ACTH-dependent forms is crucial for determining treatment options. Plasma ACTH levels aid in the differential diagnosis, with undetectable or low levels suggesting ACTH-independent hypercortisolemia. ACTH is derived from pro-opiomelanocortin, and its processing involves prohormone convertase 1/3. High-molecular-weight ACTH is generally found in ACTH-producing pituitary tumors and ectopic ACTH syndrome. The mechanism of negative feedback and the process of high-molecular-weight ACTH alternation during ACTH-independent Cushing's syndrome remain unclear. A 40-year-old woman with hypertension and multiple fractures developed symptoms suggestive of Cushing's syndrome. Computed tomography revealed a left adrenocortical tumor along with atrophy of the right adrenal gland. ACTH levels were undetectable at the previous clinic, indicating ACTH-independent Cushing's syndrome. However, subsequent measurements at our hospital revealed non-suppressed ACTH (18.1 pg/mL), prompting further investigation. Gel exclusion chromatography confirmed the presence of high-molecular-weight ACTH. Metyrapone treatment decreased the cortisol levels. In this situation, in which ACTH levels should be elevated, a decrease in high-molecular-weight ACTH levels was observed. Histological findings revealed cortisol-producing adenoma without ACTH expression. This case highlights the importance of assay differences in evaluating ACTH concentrations and introduces a novel finding of circulating high-molecular-weight ACTH. The observed decline in high-molecular-weight ACTH levels suggests a potential time lag in the negative feedback within the hypothalamic-pituitary-adrenal axis exhibited by glucocorticoids. This temporal aspect of the regulation of ACTH-related molecules warrants further exploration to enhance our understanding of the hypothalamic-pituitary-adrenal axis feedback mechanism.

Pitfalls in the lab assessment of hypopituitarism

The diagnostic approach to hypopituitarism involves many disciplines. Clinical symptoms rarely are specific. Imaging techniques are helpful but cannot prove the specific functional defects. Therefore, the definitive diagnosis of pituitary insufficiency is largely based on laboratory tests. However, also laboratory methods come with inherent limitations, and it is essential for the clinician to know and recognize typical pitfalls. Most factors potentially impairing the quality of hormone measurements are introduced in the preanalytical phase, i.e. before the hormones are measured by the laboratory. For example, the timing of blood drawing with respect to circadian rhythm, stress, and medication can have an influence on hormone concentrations. During the actual analysis of the hormones, cross-reactions with molecules present in the sample presenting the same or similar epitopes than the intended analyte may affect immunoassays. Interference can also come from heterophilic or human anti-animal antibodies. Unexpected problems can also be due to popular nutritional supplements which interfere with the measurement procedures. An important example in this respect is the interference from biotin. It became only clinically visible when the use of this vitamin became popular among patients. The extreme serum concentrations reached when patients take it as a supplement can lead to incorrect measurements in immunoassays employing the biotin-streptavidin system. To some extent, hormone analyses using liquid chromatography mass spectrometry (LCMS) can overcome problems, although availability and cost-effectiveness of this method still imposes restrictions. In the post-analytical phase, appropriateness of reference intervals and cut-offs with respect to the specific analytical method used is of outmost importance. Furthermore, for interpretation, additional biological and pharmacological factors like BMI, age and concomitant diseases must be considered to avoid misinterpretation of the measured concentrations. It is important for the clinician and the laboratory to recognize when one or more laboratory values do not match the clinical picture. In an interdisciplinary approach, the search for the underlying cause should be initiated.

Detecting the interferences in adrenocorticotropic hormone measurement - three cases reinforcing the efficiency of the complementary clinical and laboratory audit

Accurate measurement of adrenocorticotropic hormone (ACTH) is crucial in the evaluation of pituitary and adrenal disorders. Although great progress has been achieved in ACTH measurement with immunometric assays, interference may occur and adversely affect the clinical management. The report contributes to compiling the evidence on the clinical challenges with the management of the interferences in the ACTH measurement by presenting three cases: two with clinically overt hypercortisolism and discrepant ACTH concentrations within the reference interval; the third case describes the falsely elevated ACTH in a patient with secondary adrenal insufficiency. In all patients, the results obtained with the two immunometric platforms, chemiluminescence (CLIA) immunoassay (Siemens, Immulite) and electrochemiluminescence (ECLIA) immunoassay (Roche, Cobas), were discordant. Serial dilution of plasma samples revealed nonlinearity. After polyethylene glycol (PEG) precipitation recoveries were less than 22%, 26%, and 3%, respectively, supporting interference. Moreover, a decrease in ACTH concentration after incubation in a heterophile antibody-blocking tube was observed in the second case. In the first case, misinterpretation of ACTH led to inferior petrosal sinus sampling (IPSS), whereas timely detection of assay interference prevented further investigations in other cases. Increasing awareness regarding ACTH interference and comprehensive approach in evaluation could allow timely detection, helping to prevent unnecessary testing and perplexing clinical outcomes.

Immunoassay interferences: laboratory pitfall in the diagnosis of adrenocortical carcinoma

A woman in her late 50s with recent onset of hypertension, diabetes, lumbar pain and unintentional weight loss was diagnosed with a cortisol and androgen-producing adrenal mass. Despite this, serum adrenocorticotropic hormone (ACTH) concentration was inappropriately elevated, which was investigated thoroughly. Investigations included a brain magnetic resonance imaging to exclude concomitant pituitary adenoma, a corticotropin-releasing hormone stimulation test and a gallium-68 DOTATATE and 18F-FDOPA PET scan, both excluding ectopic ACTH production. Considering the disparity between clinical presentation and biochemical results, the ACTH was reanalysed using the Cobas immunoassay (Roche, Switzerland), ultimately unveiling the cause for ACTH elevation. ACTH levels had previously been measured with ACTH Immulite (Siemens, Germany), a two-site immunoassay which is prone to interferences causing falsely elevated ACTH concentrations. Inaccurate laboratory levels can lead to diagnosis delay and unnecessary diagnostic procedures and a close communication between the physicians and laboratorians is of utmost importance.

Recognition of Nonneoplastic Hypercortisolism in the Evaluation of Patients With Cushing Syndrome

The evaluation of suspected hypercortisolism is one of the most challenging problems in medicine. The signs and symptoms described by Dr Harvey Cushing are common and often create diagnostic confusion to even experienced endocrinologists. Cushing syndrome is classically defined as neoplastic hypercortisolism resulting from an ACTH-secreting tumor or from autonomous secretion of excess cortisol associated with benign or malignant adrenal neoplasia. The increasing recognition of the negative cardiometabolic effects of mild cortisol excess without overt physical signs of Cushing syndrome has led to more screening for endogenous hypercortisolism in patients with adrenal nodular disease, osteoporosis, and the metabolic syndrome. However, sustained or intermittent activation of the dynamic hypothalamic-pituitary-adrenal axis caused by chemical (alcohol), inflammatory (chronic kidney disease), psychologic (major depression), and physical (starvation/chronic intense exercise) stimuli can result in clinical and/or biochemical features indistinguishable from neoplastic hypercortisolism. Nonneoplastic hypercortisolism (formerly known as pseudo-Cushing syndrome) has been recognized for more than 50 years and often causes diagnostic uncertainty. This expert consultation describes two patients with features of Cushing syndrome who were referred for inferior petrosal sinus sampling for the differential diagnosis of ACTH-dependent hypercortisolism. Both patients were discovered to have nonneoplastic hypercortisolism: one from a covert alcohol use disorder and the other to chronic kidney disease. This consultation emphasizes the value of a good history and physical examination, appropriate laboratory testing, and the desmopressin acetate stimulation test to aid in distinguishing neoplastic from nonneoplastic hypercortisolism.

Alcohol-induced Cushing syndrome: report of eight cases and review of the literature

Introduction

Alcohol-induced hypercortisolism (AIH) is underrecognized and may masquerade as neoplastic hypercortisolism [Cushing syndrome (CS)] obscuring its diagnosis.

Objective and methods

In order to characterize AIH, we performed a chart review of eight patients (4 males and 4 females; 2014-2022) referred for evaluation and treatment of neoplastic hypercortisolism - six for inferior petrosal sinus sampling, one due to persistent CS after unilateral adrenalectomy, and one for pituitary surgery for Cushing disease (CD). Five underwent dDAVP stimulation testing.

Results

All eight patients had clinical features of hypercortisolism and plasma ACTH levels within or above the reference interval confirming hypothalamic-pituitary mediation. All had abnormal low-dose dexamethasone suppression test and increased late-night salivary cortisol. Only one had increased urine cortisol excretion. In contrast to CD, the 5 patients tested had blunted or absent ACTH and cortisol responses to desmopressin. Two had adrenal nodules and one had abnormal pituitary imaging. Most patients underreported their alcohol consumption and one denied alcohol use. Elevated blood phosphatidyl ethanol (PEth) was required in one patient to confirm excessive alcohol use. All patients had elevations of liver function tests (LFTs) with AST>ALT.

Conclusion

AIH is an under-appreciated, reversible cause of non-neoplastic hypercortisolism that is indistinguishable from neoplastic CS. Incidental pituitary and adrenal imaging abnormalities as well as under-reporting of alcohol consumption further confound the diagnosis. Measurement of PEth helps to confirm an alcohol use disorder. Elevations of LFTs (AST>ALT) and subnormal ACTH and cortisol responses to dDAVP help to distinguish AIH from neoplastic hypercortisolism.

Distinct serum steroid profiles between adrenal Cushing syndrome and Cushing disease

Background

Differentiating between adrenal Cushing syndrome (adrenal CS) and Cushing disease (CD) can be challenging if there are equivocal or falsely elevated adrenocorticotropic hormone (ACTH) values. We aim to investigate the diagnostic value of serum steroid profiles in differentiating adrenal CS from CD.

Method

A total of 11 serum steroids in adrenal CS (n = 13) and CD (n = 15) were analyzed by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Age- and gender-specific steroid ratios were generated by dividing the actual steroid concentration by the upper limit of the relevant reference range. A principal component analysis (PCA) and an orthogonal partial least squares discriminant analysis (OPLS-DA) were performed.

Results

The PCA and OPLS-DA analyses showed distinct serum steroid profiles between adrenal CS and CD. Dehydroepiandrosterone sulfate (DHEA-S), dehydroepiandrosterone (DHEA), and androstenedione ratios were identified as biomarkers for discrimination by variable importance in projection (VIP) in combination with t-tests. The sensitivity and specificity of DHEA-S ratios <0.40 were 92.31% (95% CI 64.0%-99.8%) and 93.33% (95% CI 68.1%-99.8%), respectively, in identifying adrenal CS. The sensitivity and specificity of DHEA ratios <0.18 were 100% (95% CI 75.3%-100.0%) and 100% (95% CI 78.2%-100.0%), respectively, in identifying adrenal CS.

Conclusion

Our data support the clinical use of the DHEA-S and DHEA ratios in the differential diagnosis of adrenal CS and CD, especially when falsely elevated ACTH is suspected.

The hypothalamus-pituitary-adrenal axis in sepsis- and hyperinflammation-induced critical illness: Gaps in current knowledge and future translational research directions

The classical model of the vital increase in systemic glucocorticoid availability in response to sepsis- and hyperinflammation-induced critical illness is one of an activated hypothalamus-pituitary-adrenocortical axis. However, research performed in the last decade has challenged this rather simple model and has unveiled a more complex, time-dependent set of responses. ACTH-driven cortisol production is only briefly increased, rapidly followed by orchestrated peripheral adaptations that maintain increased cortisol availability for target tissues without continued need for increased cortisol production and by changes at the target tissues that guide and titrate cortisol action matched to tissue-specific needs. One can speculate that these acute changes are adaptive and that treatment with stress-doses of hydrocortisone may negatively interfere with these adaptive changes. These insights also suggest that prolonged critically ill patients, treated in the ICU for several weeks, may develop central adrenal insufficiency, although it remains unclear how to best diagnose and treat this condition.

Molecular Derangements and the Diagnosis of ACTH-Dependent Cushing's Syndrome

Endogenous Cushing's syndrome (CS) is associated with morbidities (diabetes, hypertension, clotting disorders) and shortens life because of infections, pulmonary thromboembolism, and cardiovascular disease. Its clinical presentation is immensely variable, and diagnosis and treatment are often delayed. Thus, there are many opportunities for basic and clinical research leading to better tests, faster diagnosis, and optimized medical treatments. This review focuses on CS caused by excessive adrenocorticotropin (ACTH) production. It describes current concepts of the regulation of ACTH synthesis and secretion by normal corticotropes and mechanisms by which dysregulation occurs in corticotrope (termed "Cushing's disease") and noncorticotrope (so-called ectopic) ACTH-producing tumors. ACTH causes adrenal gland synthesis and pulsatile release of cortisol; the excess ACTH in these forms of CS leads to the hypercortisolism of endogenous CS. Again, the differences between healthy individuals and those with CS are highlighted. The clinical presentations and their use in the interpretation of CS screening tests are described. The tests used for screening and differential diagnosis of CS are presented, along with their relationship to cortisol dynamics, pathophysiology, and negative glucocorticoid feedback regulation in the two forms of ACTH-dependent CS. Finally, several gaps in current understanding are highlighted in the hope of stimulating additional research into this challenging disorder.

Clinical Study and Systematic Review of Pituitary Microadenomas vs. Macroadenomas in Cushing's Disease: Does Size Matter?

Background: Reports on clinical and biochemical differences between adrenocorticotropic hormone (ACTH)-secreting pituitary microadenomas and macroadenomas are limited and inconsistent. Objective: Compare clinical and biochemical characteristics of patients with corticotroph microadenomas and macroadenomas and assess predictive factors for biochemical response to dynamic testing for Cushing’s disease (CD) in a clinical trial and a systematic review. A second aim was to evaluate differences between macroadenomas with and without cavernous and sphenoid sinus invasion. Methods: Retrospective charts review of patients with CD, treated at Rabin Medical Center between 2000 and 2020 or at Maccabi Healthcare Services in Israel between 2005 and 2017. Clinical and biochemical factors were compared between patients with corticotroph microadenomas and macroadenomas. We have also performed a systematic review of all studies (PRISMA guidelines) comparing corticotroph microadenomas with macroadenomas up to 31 November 2021. Results: The cohort included 105 patients (82 women, 78%; mean age, 41.5 ± 14.5 years), including 80 microadenomas (mean size, 5.2 ± 2.2 mm) and 25 macroadenomas (mean size, 18.0 ± 7.7 mm). Other baseline characteristics were similar between groups. Most common presentation suggestive for hypercortisolemia among patients with both micro- and macroadenomas were weight gain (46.3% vs. 48.0%, p = NS) and Cushingoid features (27.5% vs. 20.0%, p = NS). Mean 24 h urinary free cortisol (5.2 ± 5.4 × ULN vs. 7.8 ± 8.7 × ULN) and serum cortisol following low-dose dexamethasone (372.0 ± 324.5 vs. 487.6 ± 329.8 nmol/L), though higher for macroadenomas, were not significant. Levels of ACTH were greater for macroadenomas (1.9 ± 1.2 × ULN vs. 1.3 ± 0.8 × ULN, respectively, p = 0.01). Rates of recurrent/persistent disease were similar, as were rates of post-operative adrenal insufficiency and duration of post-operative glucocorticoid replacement. Macroadenomas with sphenoid or cavernous sinus invasion were associated with higher ACTH, 24 h free urinary cortisol, and serum cortisol following low-dose dexamethasone, compared with suprasellar or intrasellar macroadenomas. Conclusions: While ACTH-secreting macroadenomas exhibit higher plasma ACTH than microadenomas, there was no association between tumor size with cortisol hypersecretion or clinical features of hypercortisolemia. Though overall rare, increased awareness is needed for patients with CD with tumor extension in the cavernous or sphenoid sinus, which displays increased biochemical burden, highlighting that extent/location of the adenoma may be more important than size per se. Our systematic review, the first on this topic, highlights differences and similarities with our study.

Clinical Spectrum of Adrenal Cushing's Syndrome and the Caution for Interpretation of Adrenocorticotrophic Hormone: A Single-Center Experience

To describe the differences in presentation, biochemistry, and radiological evaluation of various etiologies of adrenal Cushing's syndrome (CS) from a single center. To emphasize caution for interpretation of plasma adrenocorticotropic hormone (ACTH), as a spuriously unsuppressed ACTH level by immunometric assay may lead to therapeutic misadventures in adrenal CS.

DESIGN

 Retrospective, single-center, observational study.

METHODS

  Fifty-eight adrenal CS patients [Adrenocortical carcinoma (ACC), n=30; Adenoma (ACA), n=15; Primary pigmented nodular adrenocortical disease (PPNAD), n=10; ACTH independent macronodular adrenal hyperplasia (AIMAH), n=3) evaluated at a tertiary care center in western India between January 2006 to March 2020 were included. Data on demography, clinical evaluation, biochemistry, imaging, management, histopathology, and outcome were recorded in a standard format and analyzed.

RESULTS

  Cortisol secreting ACC presented at 38(1-50) years with abdominal mass in 26/30 (86.7%) and 16/30 (53.3%) had metastases at presentation. ACA with autonomous cortisol excess presented at 25(4.9-40) years with discriminating features of CS in 14/15 (93.3%), sex steroid production in 2/15, unenhanced HU <10 in only one, and relative washout >40% in 8/11 (72.7%). One ACA and eight ACC patients had plasma ACTH (by Siemens Immulite assay) > 20 pg/ml, despite hypercortisolemic state.

CONCLUSIONS

  Cortisol-secreting ACC and ACA most often present with mass effects and florid CS, respectively. Baseline HU has low sensitivity to differentiate cortisol-secreting ACA from ACC. Plasma ACTH measured by Seimens Immulite is often unsuppressed, especially in ACC patients, which can be addressed by measuring ACTH by more accurate assays.

Does concomitant prolactin measurement ıncrease the accuracy of ınferior petrosal sinus sampling?

INTRODUCTION

Prolactin (PRL) measurement during inferior petrosal sinus sampling (IPSS) can be helpful to improve the accuracy. We aimed to evaluate the effect of measuring PRL levels as a predictor for the accuracy of IPSS and evaluate its impact on the lateralization of adenomas.

METHODS

In this retrospective cohort study, we reviewed 51 patients who had undergone IPSS for the investigation of ACTH-dependent hypercortisolism.

RESULTS

Forty-nine patients had proven Cushing's disease (CD), one had EAS, and the remaining one patient had adrenal adenoma. Forty-seven patients had an above 2 ACTH IPS/P ratio at baseline, and all the post-corticotropin-releasing hormone (CRH) ACTH IPS/P ratios of patients with proven CD were above 3. In these two patients whose ACTH IPS/P ratio at baseline was below 2, PRL IPS/P ratios were above 1.8 in only the dominant side, which was considered secondary to a prolactin intersinus gradient due to the biological effects of the tumor. PRL-adjusted ACTH IPS/P ratios were > 1.3 in all patients with proven CD; it was 0.7 in the patient with EAS. Surgically confirmed positive lateralization was observed in 55.1% of patients with the ACTH gradient, but when PRL-adjusted ACTH IPS/IPS ratios were used in addition to the ACTH gradient, the ratio increased to 67.3%.

CONCLUSION

Although PRL-adjusted ACTH IPS/P ratios can be helpful to improve the accuracy of results during IPSS procedures, a prolactin intersinus gradient towards the ACTH-dominant side in patients with CD may invalidate PRL as an indicator of pituitary venous outflow.

A Pitfall of Falsely Elevated ACTH: A Case Report and Literature Review

A 35-year-old woman with unintentional weight gain, hyperpigmentation of bilateral palms, and general fatigue was initially suspected of Cushing’s syndrome or adrenal insufficiency based on the isolated elevation of the plasma adrenocorticotropic hormone (ACTH) level (113.0 pg/mL) in the Siemens ACTH Immulite assay (ACTH [Immulite]). However, both of the diagnoses were excluded by screening tests including the overnight dexamethasone suppression test, the 24-hour urinary free cortisol excretion, and the ACTH stimulation test in spite of the consistent elevation of the plasma ACTH levels. We speculated that the existence of the immunoassay interference may be the underlying cause because the plasma ACTH level analyzed by the CIS Bio International ELSA-ACTH immunoassay (ELSA-ACTH) was within the normal range. After reviewing our case and several reported cases of falsely elevated plasma ACTH levels, we conclude that when discrepancy between clinical symptoms and laboratory measurements exists, medical practitioners ought to rely on formal diagnostic criteria rather than misleading laboratory results to avoid misdiagnosis or even unnecessary invasive testing and procedures. In addition, current methods for investigation and elimination of immunoassay interferences should be applied with caution due to variable efficacy and inevitable deviations.

Outcome of CRH stimulation test and overnight 8 mg dexamethasone suppression test in 469 patients with ACTH-dependent Cushing's syndrome

OBJECTIVE

To evaluate diagnostic accuracy of the corticotropin-releasing hormone (CRH) stimulation test and the overnight 8 mg dexamethasone suppression test (DST) for the differentiation of Cushing's disease (CD) and ectopic Cushing's syndrome (ECS).

METHODS

Retrospective study in 6 European centers. Inclusion criteria: patients with a) overt adrenocorticotropin (ACTH)-dependent Cushing's syndrome at the time of dynamic testing, b) histopathological confirmed tumors and/or c) postoperative biochemical remission and/or adrenal insufficiency. Optimal cut-offs were calculated via receiver operating characteristic (ROC) analysis using CD as reference.

RESULTS

469 patients were analyzed [78% females; median age 43 years (IQR 19)]. CRH test and overnight 8 mg DST were performed in 420 [CD, n=394 (94%); ECS, n=26 (6%)] and 237 patients [228 CD (96%), 9 ECS (4%)]. Both tests were performed in 205 patients (44%). The post-CRH %-increase at 30 minutes of both ACTH (cut-off ≥31%, sensitivity 83%, specificity 85%, AUC 0.81) and cortisol (cut-off ≥12%, sensitivity 82%, specificity 89%, AUC 0.86) discriminated best between CD and ECS. A test duration of >60 minutes did not improve diagnostic performance of the CRH test. The optimal cortisol cut-off for the %-suppression during the 8 mg DST was ≥55% (sensitivity 80%, specificity 78%, AUC 0.75).

CONCLUSION

The CRH test has equivalent sensitivity but higher specificity than the 8 mg DST and is therefore the test of first choice. The diagnostic outcome of ACTH and cortisol is well comparable, however, sampling beyond 60 minutes post-CRH does not provide diagnostic benefits.

Consideration triggered by the choice of heterophilic antibody interference detection tests in measuring ACTH for a teenager boy with a rare adrenal disease

BACKGROUND

Plasma ACTH is an important marker for Cushing syndrome; inaccurate measurement of ACTH concentrations due to the serum heterophile antibody may mislead diagnosis by physicians. We describe the case of a teenage boy with a rare adrenal disease who presented falsely increased ACTH concentrations (20.3 pg/ml; Siemens Immulite).

METHODS

Low dose dexamethasone inhibition test showed no inhibition of serum cortisol. While biochemical evidence suggested ACTH-dependent Cushing, the imaging tests suggested otherwise. Hence, further tests for interference identification, including test platform replacement, sample dilution, PEG precipitation, and use of blocking antibodies, were conducted.

RESULTS

The measurements of the same patient sample on three different analytical platforms suggested ACTH concentrations below 5 pg/ml. Serial dilutions of serum samples revealed nonlinearity, PEG recovery resulted in ACTH concentrations dropping to < 5 pg/ml, and interferences in plasma were blocked by a heterophilic blocking reagent (21.2 vs < 5 pg/ml), suggesting that assay interference performed on Siemens Immulite led to false-positive ACTH. Finally, the boy was diagnosed with a rare type of ACTH-independent Cushing syndrome.

CONCLUSIONS

The inaccurate evaluation of ACTH misled the physicians, increasing treatment time and diagnostic testing. Thus, an anti-interference workflow should be established between physicians and laboratories to avoid such cases in the future.

Corticotroph tumor progression after bilateral adrenalectomy (Nelson's syndrome): systematic review and expert consensus recommendations

BACKGROUND

Corticotroph tumor progression (CTP) leading to Nelson's syndrome (NS) is a severe and difficult-to-treat complication subsequent to bilateral adrenalectomy (BADX) for Cushing's disease. Its characteristics are not well described, and consensus recommendations for diagnosis and treatment are missing.

METHODS

A systematic literature search was performed focusing on clinical studies and case series (≥5 patients). Definition, cumulative incidence, treatment and long-term outcomes of CTP/NS after BADX were analyzed using descriptive statistics. The results were presented and discussed at an interdisciplinary consensus workshop attended by international pituitary experts in Munich on October 28, 2018.

RESULTS

Data covered definition and cumulative incidence (34 studies, 1275 patients), surgical outcome (12 studies, 187 patients), outcome of radiation therapy (21 studies, 273 patients), and medical therapy (15 studies, 72 patients).

CONCLUSIONS

We endorse the definition of CTP-BADX/NS as radiological progression or new detection of a pituitary tumor on thin-section MRI. We recommend surveillance by MRI after 3 months and every 12 months for the first 3 years after BADX. Subsequently, we suggest clinical evaluation every 12 months and MRI at increasing intervals every 2-4 years (depending on ACTH and clinical parameters). We recommend pituitary surgery as first-line therapy in patients with CTP-BADX/NS. Surgery should be performed before extrasellar expansion of the tumor to obtain complete and long-term remission. Conventional radiotherapy or stereotactic radiosurgery should be utilized as second-line treatment for remnant tumor tissue showing extrasellar extension.

New Cutoffs for the Biochemical Diagnosis of Adrenal Insufficiency after ACTH Stimulation using Specific Cortisol Assays

Context

The normal cortisol response 30 or 60 minutes after cosyntropin (ACTH_[1-24]) is considered to be ≥18 μg/dL (500 nmol/L). This threshold is based on older serum cortisol assays. Specific monoclonal antibody immunoassays or LC-MS/MS may have lower thresholds for a normal response.

Objective

To calculate serum cortisol cutoff values for adrenocorticotropic hormone (ACTH) stimulation testing with newer specific cortisol assays.

Methods

Retrospective analysis of ACTH stimulation tests performed in ambulatory and hospitalized patients suspected of adrenal insufficiency (AI). Serum samples were assayed for cortisol in parallel using Elecsys I and Elecsys II immunoassays, and when volume was available, by Access immunoassay and LC-MS/MS.

Results

A total of 110 patients were evaluated. Using 18 μg/dL as the cortisol cutoff after ACTH stimulation, 14.5%, 29%, 22.4%, and 32% of patients had a biochemical diagnosis of AI using the Elecsys I, Elecsys II, Access, and LC-MS/MS assays, respectively. Deming regressions of serum cortisol were used to calculate new cortisol cutoffs based on the Elecsys I cutoff of 18 μg/dL. For 30-minute values, new cutoffs were 14.6 μg/dL for Elecsys II, 14.8 μg/dL for Access, and 14.5 μg/dL for LC-MS/MS. Baseline cortisol <2 μg/dL was predictive of subnormal stimulated cortisol values.

Conclusion

To reduce false positive ACTH stimulation testing, we recommend a new serum cortisol cutoff of 14 to 15 μg/dL depending on the assay used (instead of the historical value of 18 μg/dL with older polyclonal antibody assays). Clinicians should be aware of the new cutoffs for the assays available to them when evaluating patients for AI.

Case Report: Consecutive Adrenal Cushing's Syndrome and Cushing's Disease in a Patient With Somatic CTNNB1, USP8, and NR3C1 Mutations

The occurrence of different subtypes of endogenous Cushing's syndrome (CS) in single individuals is extremely rare. We here present the case of a female patient who was successfully cured from adrenal CS 4 years before being diagnosed with Cushing's disease (CD). The patient was diagnosed at the age of 50 with ACTH-independent CS and a left-sided adrenal adenoma, in January 2015. After adrenalectomy and histopathological confirmation of a cortisol-producing adrenocortical adenoma, biochemical hypercortisolism and clinical symptoms significantly improved. However, starting from 2018, the patient again developed signs and symptoms of recurrent CS. Subsequent biochemical and radiological workup suggested the presence of ACTH-dependent CS along with a pituitary microadenoma. The patient underwent successful transsphenoidal adenomectomy, and both postoperative adrenal insufficiency and histopathological workup confirmed the diagnosis of CD. Exome sequencing excluded a causative germline mutation but showed somatic mutations of the β-catenin protein gene (CTNNB1) in the adrenal adenoma, and of both the ubiquitin specific peptidase 8 (USP8) and the glucocorticoid receptor (NR3C1) genes in the pituitary adenoma. In conclusion, our case illustrates that both ACTH-independent and ACTH-dependent CS may develop in a single individual even without evidence for a common genetic background.

The definition of remission and recurrence of Cushing's disease

Accurate classification of postsurgical remission, and early recognition of recurrence are crucial to timely treat and prevent excess mortality in Cushing's Disease, yet the criteria used to define remission are variable and there is no consensus to define recurrence. Remission is defined as postsurgical hypocortisolemia, but delayed remission may occur. Recurrence is the return of clinical manifestations with biochemical evidence of hypercortisolism. The proper combination of tests and their timing are controversial. Reliable predicting tools may lead to earlier diagnosis upon recurrence. Many factors have been studied independently for prediction with variable performance. Novel artificial intelligence approaches seek to integrate these variables into risk calculators and machine-learning algorithms with an acceptable short-term predictive performance but lack longer-term accuracy. Prospective studies using these approaches are needed. This review summarizes the evidence behind the definitions of remission and recurrence and provide an overview of the available tools to predict and/or diagnose them.

ADRENOCORTICOTROPIC HORMONE IMMUNOASSAY INTERFERENCE IN A PATIENT WITH SUBCLINICAL HYPERCORTISOLISM

Context

Immunoassays are vulnerable to occasional analytical errors despite their sensitivity and specificity. Adrenocorticotropic hormone (ACTH) is among hormones which are vulnerable to assay interference.

Objective

In this case report, we aimed to present a case of ACTH interference in a patient with subclinical hypercortisolism.

Case report

We present a case of subclinical hypercortisolism with unexpectedly elevated levels of ACTH in whom interference was shown by different biochemical methods.It is important for the clinician to keep in mind the possibility of interference when clinical and laboratory results are discordant. The communication between the clinician and laboratory staff is important while interpreting results. This case report shows that ACTH interference should be considered in patients with subclinical hypercortisolism who have unexpectedly high levels of adrenocorticotropic hormone.

American Association of Clinical Endocrinology Disease State Clinical Review on the Evaluation and Management of Adrenocortical Carcinoma in an Adult: a Practical Approach

OBJECTIVE

The aim of this Disease State Clinical Review is to provide a practical approach to patients with newly diagnosed adrenocortical carcinoma, as well as to follow-up and management of patients with persistent or recurrent disease.

METHODS

This is a case-based clinical review. The provided recommendations are based on evidence available from randomized prospective clinical studies, cohort studies, cross-sectional and case-based studies, and expert opinions.

RESULTS

Adrenocortical carcinoma is a rare malignancy, often with poor outcomes. For any patient with an adrenal mass suspicious for adrenocortical carcinoma, the approach should include prompt evaluation with detailed history and physical exam, imaging, and biochemical adrenal hormone assessment. In addition to adrenal-focused imaging, patients should be evaluated with chest-abdomen-pelvis cross-sectional imaging to define the initial therapy plan. Patients with potentially resectable disease limited to the adrenal gland should undergo en bloc open surgery by an expert surgeon. For patients presenting with advanced or recurrent disease, a multidisciplinary approach considering curative repeat surgery, local control with surgery, radiation therapy or radiofrequency ablation, or systemic therapy with mitotane and/or cytotoxic chemotherapy is recommended.

CONCLUSION

As most health care providers will rarely encounter a patient with adrenocortical carcinoma, we recommend that patients with suspected adrenocortical carcinoma be evaluated by an expert multidisciplinary team which includes clinicians with expertise in adrenal tumors, including endocrinologists, oncologists, surgeons, radiation oncologists, pathologists, geneticists, and radiologists. We recommend that patients in remote locations be followed by the local health care provider in collaboration with a multidisciplinary team at an expert adrenal tumor program.

ABBREVIATIONS

ACC = adrenocortical carcinoma; ACTH = adrenocorticotropic hormone; BRACC = borderline resectable adrenocortical carcinoma; CT = computed tomography; DHEAS = dehydroepiandrosterone sulfate; EDP = etoposide, doxorubicin, cisplatin; FDG = ¹⁸F-fluorodeoxyglucose; FNA = fine-needle aspiration; HU = Hounsfield units; IVC = inferior vena cava; LFS = Li-Fraumeni syndrome; MEN1 = multiple endocrine neoplasia type 1; MRI = magnetic resonance imaging; OAC = oncocytic adrenocortical carcinoma; PC = palliative care; PET = positron emission tomography.

Calcium Stimulation Test for Insulinoma Localization in an End-stage Renal Disease Patient on Diazoxide

Insulinomas are rare, and even rarer in patients with end-stage renal disease (ESRD). Clear criteria for the biochemical diagnosis of insulinomas in patients with renal failure have not been established, and hypoglycemia is often attributed to the renal disease itself, frequently leading to a delay in diagnosis. We describe a case of a patient who presented with asymptomatic recurrent hypoglycemia during hemodialysis. Disease progression and biochemical testing strongly suggested an insulinoma. Computed tomography (CT) of the abdomen and pelvis, ¹¹¹In-pentetreotide scintigraphy and endoscopic ultrasound did not localize a pancreatic tumor. A calcium stimulation test was performed while the patient was taking diazoxide due to severe hypoglycemia with fasting for a couple of hours without treatment. The test showed a marked increase in insulin after calcium infusion in the dorsal pancreatic artery, localizing the tumor to the body and tail of the gland. Exploratory surgery easily identified a tumor at the body of the pancreas and pathology confirmed an insulin-secreting pancreatic neuroendocrine tumor. On follow-up, there was resolution of the hypoglycemia. We review the challenges of diagnosing an insulinoma in ESRD and describe a successful intra-arterial calcium stimulation test done in an ESRD patient while continuing diazoxide.

Impaired dexamethasone resorption in two patients with pseudo-Cushing after bariatric surgery: Implications for immunosuppressive treatment

Two cases of middle-aged female patients treated by gastric bypass surgery for weight loss presented to our clinic for a follow-up examination 3-6 months after the surgical procedure (a mini gastric bypass and a modified single anastomosis sleeve-ileostomy). In both patients increased ACTH levels and either high serum cortisol or an increased urinary cortisol excretion was apparent and triggered further endocrine testing. Serum cortisol could not be suppressed adequately by 2 and 4 mg dexamethasone in the standardized oral overnight suppression test while midnight salivary cortisol dropped well below the desired cut-off. This led to the hypothesis of an impaired dexamethasone resorption and could be further substantiated by suppression of serum cortisol below the cut-off by an intravenous dexamethasone application. The data presented point to an impairment of enteral synthetic corticosteroid resorption in patients after gastric bypass surgery and could be of importance for individuals in need for immunosuppressive treatment. In view of the growing number of bariatric procedures, pharmacokinetics of corticosteroids and other drugs should be tested in clinical trials.

Incidentally detected sellar spine in a patient with Cushing's syndrome: a case report

Sellar spine, a bony spur extending anteriorly from the dorsum sellae, is a very rare anatomical variant. Several hypotheses regarding its etiology have been proposed, including the strongly supported theory of a cephalic ossified notochordal remnant. Sellar spine is usually detected incidentally in patients who have no definite symptoms, but several cases have reportedly accompanied endocrinopathies such as precocious puberty, hypopituitarism, or galactorrhea/oligomenorrhea. However, no published reports have described sellar spine in a patient with Cushing’s syndrome. We herein report a case of sellar spine detected during the evaluation of Cushing’s disease in a 29-year-old woman who underwent inferior petrosal sinus sampling, computed tomography, magnetic resonance imaging, and exploratory surgery. There was no evidence of a pituitary microadenoma, but a sellar spine was present in the operative field. Thus, the sellar spine might have caused Cushing’s syndrome in this case, although the exact mechanism is unknown.

The Optimal Cut-off of BIPSS in Differential Diagnosis of ACTH-dependent Cushing's Syndrome: Is Stimulation Necessary?

CONTEXTS

Bilateral inferior petrosal sinus sampling (BIPSS) can differentiate Cushing's disease (CD) and ectopic adrenocorticotropin (ACTH) syndrome (EAS). The traditional cutoff of inferior petrosal sinus to peripheral (IPS:P) ACTH gradient was 2 before stimulation and 3 after stimulation, which yielded unsatisfactory sensitivity in some studies.

OBJECTIVES

To determine the optimal cutoff in BIPSS before or after desmopressin stimulation and to evaluate the necessity of stimulation.

DESIGN AND SETTING

Single-center retrospective study (2011-2018) along with meta-analysis.

PATIENTS

226 CD and 24 EAS patients with confirmed diagnosis who underwent BIPSS with desmopressin stimulation.

RESULTS

In the meta-analysis of 25 studies with 1249 CD and 152 EAS patients, the traditional cutoff yielded sensitivity of 86% and 97% and specificity of 98% and 100% before and after stimulation, respectively. We then analyzed the data from our center. With the traditional cutoff, the sensitivity was 87.2% (197/226) and 96.5% (218/226) before and after stimulation, and specificity was both 100% (25/25), which were close to the results of meta-analysis. Receiver operating characteristic analysis revealed that the optimal cutoff was 1.4 before stimulation and 2.8 after stimulation. With the new cutoff, the sensitivity was 94.7% (214/226) and 97.8% (221/226) while the specificity remained 100% (25/25) before and after stimulation. Among the 7 CD patients (7/226; 3.1%) for whom stimulation was necessary to get correct diagnosis, none has a pituitary lesion >6 mm by magnetic resonance imaging, and their sampling lateralization rate (P = .007) and peak ACTH level at dominant inferior petrosal sinus (P = .011) were lower than those among CD patients with IPS:P >1.4 before stimulation.

CONCLUSIONS

The optimal cutoff for IPS:P in BIPSS is different from the commonly-used one. The optimal cutoff value can yield satisfactory accuracy even without stimulation, and stimulation may be unnecessary for those with pituitary adenoma >6 mm.

Adrenal insufficiency: Physiology, clinical presentation and diagnostic challenges

Adrenal insufficiency (AI) is a serious condition, which can arise from pathology affecting the adrenal gland itself (primary adrenal insufficiency, PAI), hypothalamic or pituitary pathology (secondary adrenal insufficiency, SAI), or as a result of suppression of the hypothalamic-pituitaryadrenal (HPA) axis by exogenous glucocorticoid therapy (tertiary adrenal insufficiency, TAI). AI is associated with an increase in morbidity and mortality and a reduction in quality of life. In addition, the most common cause of PAI, autoimmune adrenalitis, may be associated with a variety of other autoimmune disorders. Untreated AI can present with chronic fatigue, weight loss and vulnerability to infection. The inability to cope with acute illness or infection can precipitate life-threatening adrenal crisis. It is therefore a critical diagnosis to make in a timely fashion, in order to institute appropriate management, aimed at reversing chronic ill health, preventing acute crises, and restoring quality of life. In this review, we will describe the normal physiology of the HPA axis and explain how knowledge of the physiology of this axis helps us understand the clinical presentation of AI, and forms the basis for the biochemical investigations which lead to the diagnosis of AI.

An Intact ACTH LC-MS/MS Assay as an Arbiter of Clinically Discordant Immunoassay Results

BACKGROUND

Measurement of plasma adrenocorticotropic hormone (ACTH) is key in the differential diagnosis of hypothalamic-pituitary-adrenal disorders. Two-site sandwich immunoassays dominate clinical testing of ACTH in North America; however, discordant results between manufacturers have been repeatedly reported. To resolve the discrepancy, we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) assay for the intended measurand, biologically active intact ACTH (iACTH).

METHODS

The multiple reaction monitoring LC-MS/MS assay was designed to selectively measure full-length iACTH, as well as ACTH analogs and fragments (i.e., ACTH1–24 and ACTH18–39). Epitope assignment of the Roche Elecsys antibodies was performed by MALDI-TOF mass spectrometry. A method comparison between Roche Elecsys and Siemens Immulite ACTH immunoassays was performed and clinically concordant/discordant results identified. In a subset of these samples, the iACTH concentration was determined using the LC-MS/MS method.

RESULTS

The lower limit of the measuring interval of the iACTH LC-MS/MS assay was 9 pg/mL (2 pmol/L). The assay was linear from 9 to 1938 pg/mL (2 to 427 pmol/L). Epitope mapping revealed that the Roche capture and detection antibodies bound residues 9–12 and 36–39 of ACTH, respectively. The iACTH LC-MS/MS analysis demonstrated that for discordant results between 2 immunoassays studied, only the Roche results were highly positively correlated with the iACTH concentration.

CONCLUSIONS

Immunoprecipitation of biologically active ACTH molecules followed by LC-MS/MS analysis enabled selective detection of iACTH and relevant biologically active fragments in plasma. Applied to the investigation of clinically discrepant results, this method can act as an arbiter of the concentration of iACTH present.

Diagnostic utility of Gallium-68-somatostatin receptor PET/CT in ectopic ACTH-secreting tumors: a systematic literature review and single-center clinical experience

PURPOSE

Tumors causing ectopic Cushing's syndrome (ECS) are often not visible with conventional imaging. Gallium-68-DOTATATE, DOTATOC, and DOTANOC positron emission tomography/computed tomography (⁶⁸Ga-SSTR PET/CT) reportedly exhibits greater sensitivity in identifying an ECS source, however, evidence is limited to mainly case reports and a few small retrospective studies. Previous systematic ECS imaging review has shown ⁶⁸Ga-SSTR PET/CT sensitivity is similar to CT (81.8%) in histologically-proven cases and is 100% in covert-cases, however, the number of patients was small and no occult cases were reported.

METHODS

We performed a systematic literature review of ⁶⁸Ga-SSTR PET/CT use in ECS patients. We also report 6 consecutive patients with confirmed active and occult ECS who underwent ⁶⁸Ga-DOTATATE PET/CT and were followed at our institution between 2014 and 2019.

RESULTS

We identified 33 articles (23 case-reports, 4 case-series, 5 retrospective studies and 1 prospective study) detailing ⁶⁸Ga-SSTR PET/CT in 69 ECS patients. Overall ⁶⁸Ga-SSTR PET/CT sensitivity was 64.0%, while in histologically confirmed cases (67 lesions), sensitivity was 76.1%. There were two false-positives cases, both in the adrenal glands. In covert cases, ⁶⁸Ga-SSTR PET/CT identified 50% of lesions. There were ten occult cases where all imaging failed to identify an adrenocorticotropic hormone source; source remains unknown. In our case series, ⁶⁸Ga-DOTATATE PET/CT showed decreased uptake in pancreatic neuroendocrine tumor in one patient and did not help identify an ECS source in 5 patients.

CONCLUSION

Both this systematic literature review, the largest to date, and our single- center experience demonstrate a lower than previously reported ⁶⁸Ga-SSTR PET/CT sensitivity for ECS, especially in occult lesions. We suggest that the data on ⁶⁸Ga-SSTR PET/CT in ECS is subject to publication bias, and false-negatives are likely underreported; it's diagnostic value for ECS needs further study.

Hypercortisolemia Recurrence in Cushing's Disease; a Diagnostic Challenge

Cushing's disease recurrence following successful pituitary surgery is common and merits prompt and careful diagnosis, as untreated hypercortisolism leads to increased morbidity and mortality. However, an established recurrence definition has not been forthcoming. This poses a diagnostic challenge especially early in the course of returning hypercortisolemia and/or in the presence of non-neoplastic hypercortisolemia. A late-night salivary cortisol (LNSC) test is the first test to reveal abnormal results, however, has limitations related to assay performance as well as individual patient variability. Dexamethasone suppression tests and 24-h urinary free cortisol (UFC) results are next to reveal abnormal results. Other tests including, corticotropin-releasing hormone (CRH) stimulation test and combined CRH-dexamethasone test, as well as desmopressin stimulation test with/without dexamethasone are also used, although, none have proven to be the preeminent diagnostic test for recurrence determination. There is a possible role for these tests in predicting recurrence in patients who have experienced remission, though, this also remains challenging due to lack of established cutoff values. This article details and summarizes evidence about different diagnostic tests currently used to diagnose and predict Cushing's disease recurrence.