Clinical Spectrum of Adrenal Cushing’s Syndrome and the Caution for Interpretation of Adrenocorticotrophic Hormone: A Single- Center Experience
Authors
Vikrant Gosavi1 , Anurag Lila1, Saba Samad Memon1, Vijaya Sarathi2, Kunal Thakkar3, Abhay Dalvi4, Gaurav Malhotra5, Gagan Prakash6, Virendra Patil1, Nalini S. Shah1, Tushar Bandgar1
Affiliations
1 Department of Endocrinology, Seth G. S. Medical College and KEM Hospital, Mumbai, India
2 Department of Endocrinology, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, India
3 Sterling Ramkrishna Speciality Hospital, Gandhidham, India
4 Department of Surgery, Seth G. S. Medical College and KEM Hospital, Mumbai, India
5 Department of Nuclear Medicine, Bhabha Atomic Research Centre, Mumbai, India
6 Department of Uro-oncology, Tata Memorial Hospital, Mumbai, India
Key words
adrenal Cushing’s syndrome, adrenocorticotrophic hormone, Cushing’s syndrome, adrenocortical carcinoma
received 31.08.2021 accepted after revision 03.01.2022
Bibliography
Horm Metab Res 2022; 54: 57-66 DOI 10.1055/a-1735-3232 ISSN 0018-5043
@ 2022. Thieme. All rights reserved. Georg Thieme Verlag, Rüdigerstraße 14, 70469 Stuttgart, Germany
Correspondence
Dr. Anurag Lila Department of Endocrinology 103, 1st Floor OPD Building KEM Hospital Campus Parel 400012 Mumbai Maharashtra India Tel .: +91/800/7774 385 anuraglila@gmail.com
ABSTRACT
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. De- sign: Retrospective, single-center, observational study. Meth- ods: Fifty-eight adrenal CS patients [Adrenocortical carcino- ma (ACC), n= 30; Adenoma (ACA), n = 15; Primary pigmented nodular adrenocortical disease (PPNAD), n = 10; ACTH inde- pendent 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 demog- raphy, clinical evaluation, biochemistry, imaging, manage- ment, histopathology, and outcome were recorded in a stand- ard 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 sensi- tivity 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 measur- ing ACTH by more accurate assays.
Introduction
Endogenous Cushing’s syndrome (CS) is characterized by excess and unregulated cortisol secretion leading to adverse clinical out- comes. Hypersecretion of cortisol may be driven either by an ex- cessive adrenocorticotrophic hormone (ACTH) from the pituitary/ ectopic source or by a primary adrenal pathology - adrenal CS. Ad- renal CS is a less frequent cause of CS, accounting for 20% of adult patients, whereas it is more common in children (50% in chil- dren<7 years of age) [1, 2]. Unilateral pathology (tumor) is pre- dominant, whereas bilateral pathology (hyperplasia) accounts for a smaller proportion of patients. Adrenocortical carcinoma (ACC) has a bimodal age distribution (first and 5-6th decade), whereas adrenocortical adenoma (ACA) is more prevalent in the 4-5th dec- ade [3]. Bilateral causes also have age predilection with primary pigmented nodular adrenocortical disease (PPNAD) manifesting in the first three decades and primary bilateral macronodular adrenal hyperplasia (PBMAH) presenting in the 5-6th decade [4]. Under- standing the differences in presentation, biochemistry, and radio- logical evaluation of adrenal CS is vital for their appropriate man- agement.
Measurement of plasma ACTH level by immunometric assay helps in the etiological classification of endogenous CS. Plasma ACTH level>20 pg/ml indicates ACTH-dependent CS, while ≤10pg/ml indicates ACTH-independent (adrenal) etiology. ACTH levels > 10-20 pg/ml fall in the ‘grey zone’, and an additional battery of tests is warranted for distinguishing ACTH-dependent from ACTH-independent etiologies [5, 6]. Inappropriate sample collec- tion and storage conditions may lead to falsely low ACTH levels due to degradation of this labile analyte, which may erroneously sug- gest an ACTH-independent CS. On the other hand, adrenal CS may be misdiagnosed as ACTH-dependent by an unsuppressed plasma ACTH, as reported in a few case reports/series [7-10]. Here, we de- scribe our experience of adrenal CS from a single center, empha- sizing caution for interpretation of ACTH.
Ethics Approval
The study was approved by the Institutional Ethics Committee-II (EC/OA-101/2019) of Seth GS Medical College and KEM hospital with a waiver of consent.
Patients and Methods
A retrospective data analysis of patients with adrenal CS, diagnosed and managed at our institute between January 2006 and March 2020, a tertiary referral health care center in western India, was done. The final etiological diagnosis of adrenal CS was based on his- topathology in all, except for five metastatic ACC and two PBMAH patients in whom the diagnosis was based on clinical, hormonal, and imaging characteristics. In adrenocortical tumor patients with available histopathology (surgical specimen in 36 cases and biop- sy in 4 cases), the presence of metastasis, local invasion or recur- rence, and/or a Weiss score ≥4, were used to diagnose ACC where- as in those without metastasis, local invasion or recurrence and Weiss score of ≤3, a diagnosis of ACA were made. Data on demog- raphy, clinical evaluation, biochemistry, imaging, management, histopathology, and outcomes were recorded in a standard format. In a patient presenting with adrenal mass, autonomous cortisol se-
cretion was diagnosed by an overnight dexamethasone suppres- sion test (ODST) serum cortisol value was>5 µg/dl and/or 24-hour urinary free cortisol (UFC) was more than the upper limit of normal (ULN). Patients with possible autonomous cortisol secretion (ODST cortisol 1.9-5.0 µg/dl) were excluded. Moon facies with plethora, easy bruising, wide livid striae, proximal myopathy, and weight gain with reduced growth velocity in children were considered as dis- criminatory signs of CS (DSCS) [11]. In clinically suspected CS with biochemically proven endogenous hypercortisolism and sup- pressed plasma ACTH ≤ 10 pg/ml were subjected to adrenal imag- ing. Plasma ACTH level was repeated in patients with borderline plasma ACTH (10-20 pg/ml). Contrast-enhanced CT adrenal imag- ing was performed with a 64-slice multidetector CT system (Bril- liance 64, Philips Healthcare, Best, and The Netherlands), and ab- solute and relative washout characteristics of adrenal masses were noted as per standard protocol [12]. 18F-Fluorodeoxyglucose pos- itron emission tomography-computed tomography (FDG-PET/CT) was performed as per standard protocol for patients with suspected malignancy. The highest standardized uptake value (SUVmax) was determined by software incorporated in the PET workstation. It was defined as a focal area of abnormal uptake in the region of interest (ROI) compared to the surrounding.
Patients with ACA underwent laparoscopic adrenalectomy, while adrenal tumors suspicious of ACC underwent open surgical resection. Patients with unilateral lesions who had post-surgery 8:00 AM serum cortisol level <5 µg/dl were diagnosed to have sup- pressed hypothalamic-pituitary-adrenal (HPA) axis and were re- placed with oral glucocorticoid. Patients with uncured/inoperable ACC were managed with local bed radiotherapy and/or chemotherapy regimen with etoposide, doxorubicin, and cisplatin with or without mitotane.
Cortisol was measured by a solid-phase competitive chemilu- minescent enzyme immunoassay (Siemens Healthcare) with an analytical sensitivity of 0.2 ug/dl. This assay’s intra-assay and inter- assay coefficients of variability (CV) were 6.9 and 7.3%, respective- ly. Plasma ACTH was measured on a solid-phase, two-site sequen- tial chemiluminescent assay. Immulite (Siemens Healthcare) assay has been used since 2006, and Liaison (Diasorin) was added since December 2017. The intra-assay, interassay CV, and analytical sen- sitivity were 9.6%, 8.8 %, 0.5 pg/ml, and 4.9%, 8.9%, 1.6 pg/ml for Siemens Immulite and Liaison assays, respectively. The lowest plas- ma ACTH value was considered for analysis when multiple values were available. Plasma ACTH was measured with adequate pre-an- alytic care (collection of plasma sample, maintaining a cold tem- perature, and immediate processing). Serum DHEAS was measured by Chemiluminescence Microparticle Immunoassay (CMIA) on Rosch Cobas platform with intra-assay and inter-assay (CVs) of 4 and 4.6%, respectively, and analytical sensitivity of 0.2 µg/dl. We have used the age and gender-specific normative range for serum DHEAS as described previously [13, 14].
Statistical analysis
Qualitative data were represented as frequency and percentage. Quantitative data were described using mean ± standard deviation for normally distributed data, otherwise as median with range. Association between qualitative variables was assessed by the chi-square test or Fisher’s exact test. Analysis of quantitative data
between two groups was carried out using unpaired t-test or Mann-Whitney test. For all statistical tests, p<0.05 was considered significant. Receiver operating characteristic (ROC) curve analysis was performed to differentiate ACC from ACA using tumor size and relative washout. Statistical analysis was performed using IBM SPSS Statistics (version 23.0) and MedCalc for Windows (version 19.8).
Results
Of the total endogenous CS patients (n=310), 18.7% (n=58) had adrenal CS. The characteristics of the study cohort are described in Table 1. Unilateral adrenal pathology was more common [ACC=30 (51.7%), ACA = 15 (25.9%)] compared to bilateral caus- es [PPNAD= 10 (17.2%), PBMAH=3 (5.2%)]. Patients with PPNAD were the youngest [19 (1.2-48) years], whereas those with PBMAH were the oldest [57 (30-60) years]. There was female preponder- ance, which was most marked in the ACA group. DSCS was more frequent in ACA (93.3%) and PPNAD (100%) than ACC (46.7%) and PBMAH (1/3 patient).
On comparing ACC with ACA, ACC primarily presented as ab- dominal mass (86.7%) while most ACA presented with CS (80%). ACA presented at a younger age and had female predilection. Basal and ODST serum cortisol were comparable between the two groups. Plasma ACTH levels were significantly higher (15.9±13.3 vs. 8.8 ± 12.0 pg/ml) in the ACC group than in the ACA group. Twelve patients (ACC = 10, ACA =2) had plasma ACTH levels be- tween 10 and 20 pg/ml and nine patients (ACC= 8, ACA =1) had levels >20 pg/ml.
Low serum DHEAS had a sensitivity of 54.5% (6/11) and speci- ficity of 83.3 % (15/18) for the diagnosis of ACA. Elevated serum DHEAS had a sensitivity of 50% (9/18) and specificity of 81.8% (9/11) for the diagnosis of ACC. A patient of ACA (5-year-old girl) had presented with abdominal mass (size: 5.6 cm) and also had pubarche and clitoromegaly with a serum testosterone level of 1.1 ng/ml and DHEAS level of 185.3 µg/dl (normal range: 7.4-46.8). Another 13-year-old boy with the final diagnosis of ACA (size: 5.2 cm) had presented with CS; also had gynecomastia with a serum estrogen level of 246 pg/ml and DHEAS level of 367 µg/dl (normal range: 13.6-288.9). Both these patients had a Weiss score of 3 on histo- pathological examination. Adrenal tumor size>4 cm had a sensitivity of 96.7% (29/30) and specificity of 73.3% (11/15) for the diagno- sis of ACC. This specificity increased to 100%, with a sensitivity of 93.3% (28/30) when tumor size cut off was increased to>6 cm. Basal HU was> 10, for all adrenal tumors, except one ACA (1/11, 9.1 %). Absolute washout of > 60 and ≥ 55% had sensitivities of 63.6% (7/11) and 90.9% (10/11) and specificities of 72.2% (13/18) and 66.7% (12/18), respectively, for the diagnosis of ACA. Relative washout of>40% had a sensitivity of 72.7% (8/11) and specificity of 100% (18/18) for the diagnosis of ACA. On FDG-PET/CT, the le- sion SUVmax of ACC was significantly higher than that of ACA (12.9±4.8 vs. 6.2± 1.8, p=0.019), and the ratio of lesion SUVmax to liver SUVmean was 6.5 + 2.6 (n = 10). In the ACA cohort, lesion SUVmax was 6.2 ± 1.8 (n=3), and lesion SUVmax to liver SUVmean ratio was 1.9 (n= 1). Using ROC curve analysis, a lesion size of more than of 5.4 cm had sensitivity and specificity of 93.3 and 99.93 % respectively, for the diagnosis of ACC whereas a relative washout
of more than 31.8 % had sensitivity and specificity of 90.9 and 95%, respectively, for the diagnosis of ACA.
The plasma ACTH values for adrenal CS patients are depicted in Fig. 1. One ACA and eight ACC patients had plasma ACTH of>20 pg/ml despite hypercortisolemic state as defined by ODST serum cortisol value >5 µg/dl and/or UFC>ULN (> Table 2). Repeat ACTH values were not available for these ACC patients as they had presented with abdominal pain leading to detection of large adre- nal mass (8.9-19 cm) on ultrasonogram. Of these eight ACC pa- tients, only three had DSCS. While the ACA patient with ACTH above 20 pg/ml was a 21-year-old female, presented with CS and an unsuppressed plasma ACTH (49.6 pg/ml). Her pituitary imaging was normal, and inferior petrosal sinus sampling was planned. Meanwhile, contrast-enhanced CT chest and abdomen was done to localize an obvious ectopic source, which revealed a 3.2 cm li- pid-poor (unenhanced CT density: 27 HU) left adrenal mass with relative washout of 47.1 %, with a thinned out right adrenal. She was cured after the left adrenalectomy. ACTH values in these pa- tients were obtained from the Seimens Immulite platform. In an- other five patients with initial ACTH of> 13 pg/ml (13.1-149 pg/ ml) (13.1-149 pg/ml) by Siemens Immulite assay, repeat ACTH measurements by Liaison assay were < 13 pg/ml (1.6-12.7 pg/ml).
Most ACC patients (53.3%) were of ENSAT (European Network for the Study of Adrenal Tumors) stage IV, while stage II and III com- prised 20% patients each, and only two patients presented with stage I disease. Surgery was not considered feasible in nine out of the 16 metastatic patients, of which 5 received palliative chemo- therapy. Twenty-one patients underwent open surgery followed by local bed radiotherapy (n=9) and chemotherapy (n= 13). The median survival of the ACC group was 23 (95 % CI: 3 to 43) months (Fig. 2). All ACA patients were cured following laparoscopic ex- cision of the tumor. The mean time to HPA axis recovery post-sur- gery was 10.6 ± 9.1 months.
Most (9/10) of the PPNAD patients have been described previ- ously [15]. Two patients of AIMAH presented incidentally on ab- dominal imaging, while one presented with CS. The latter, who un- derwent bilateral adrenalectomy, were cured, while the other two were managed with watchful observation (annual monitoring with 24-hour UFC) and medical therapy for comorbidities (diabetes mel- litus and hypertension).
Discussion
In our cohort, adrenal CS comprised 18.7% of all endogenous CS, with unilateral etiology (77.6%) being more common than bilateral (22.4%). We report that plasma ACTH level of > 20 pg/ml is not un- common in adrenal CS when measured by Siemens Immulite assay, especially in patients with ACC. All ACC with an ACTH of > 20 pg/ml were detected by ultrasonogram. Washout characteristics (relative washout<40%, absolute washout of <60%) and size (>5.4cm), but not baseline HU, had good diagnostic accuracy to differentiate cor- tisol- secreting ACC from ACA.
The proportion of adrenal CS amongst endogenous CS is similar to that reported in the literature ( = 20%) [1, 2, 6]. In contrast, amongst the adrenal CS, the proportion of ACC (despite being a predominant adult cohort) was more than ACA, which may be due to referral bias.
>Table 1 Baseline characteristics of adrenal Cushing’s syndrome (CS).
| Adrenocortical carcinoma n=30 | Adrenocortical adenoma n= 15 | Primary pigmented nodular adrenal hyperplasia n= 10 | Primary bilateral macronodular adrenal hyperplasia n= 3 | ||
|---|---|---|---|---|---|
| Age (years), median (range) | 38 (1-50) | 25 (4.9-40)* | 19 (1.2-48) | 57 (30-60) | |
| Gender, (Female/Male) | 17/13 | 14/1 | 6/4 | 2/1 | |
| Presentation | Abdominal mass | 26/30 (86.7%) | 1/15 (6.7%) | – | – |
| Cushing's syndrome | 4/30 (13.3%) | 12/15 (80%)* | 7/10 (70%) | 1/3 | |
| Incidental | – | 2/15 (13.3%) | – | 2/3 | |
| Family screening | – | – | 3/10 (30%) | – | |
| Discriminatory signs of CS | 14/30 (46.7%)* | 14/15 (93.3%)* | 10/10 (100%) | 1/3 | |
| - Moon facies with plethora | 14/30 (46.7%)* | 14/15 (93.3%)* | 10/10 (100%) | 1/3 | |
| - Striae/bruising | 3/30 (10%) | 10/15 (66.7%) | 4/10 (40%) | 1/3 | |
| - Muscle weakness | 6/30 (20%) | 7/15 (46.7%) | 3/10 (30%) | 2/3 | |
| - Growth failure | 1/6 (16.7%) | 2/3 (66.7%) | 6/9 (66.7%) | – | |
| Irregular menses | 5/10 (50%) | 10/13 (79.6%) | 1/2 (33.3%) | 0/1 | |
| Hirsuitism | 6/15 (40%) | 8/12 (66.7%) | 2/6 (33.3%) | 0/2 | |
| Gynecomastia | 4/13 (30.8%) | 1/1 | 0/4 | 0/1 | |
| Osteoporosis | 4/12 (33.3%) | 2/8 (25%) | 4/5 (80%) | 1/2 | |
| Diabetes mellitus | 4/30 (13.3%) | 4/15 (26.7%) | 1/10 (10%) | 1/3 | |
| Hypertension | 15/30 (50%) | 6/15 (40%) | 2/10 (20%) | 2/3 | |
| Serum potassium (mEq/l), mean ( ± SD) | 3.4 (±0.67) | 3.7 (±0.78) | 4.3 (±0.56) | 4.2 (n=1) | |
| 8 AM serum cortisol (µg/dl), mean (± SD) | 24.3 (±11.9) | 21.7 (± 12.5) | 19.6 (±7) | 18 (±6.3) | |
| ODST serum cortisol (µg/dl), Mean (± SD) | 19.6 (± 10.5) | 19 (±8.5) | 21.3 (±8.3) | 13.7 (±10.2) | |
| Plasma Adrenocorticotrophic hormone (pg/ml) | Mean ( ± SD) | 15.9 (±13.3)' | 8.8 (±12)* | 7.2(±3.7) | 4.5(±5.1) |
| Median (range) | 11.5 (1.6-52.9) | 5 (1.6-49.6) | 7.1 (1.6-12.1) | 1.6 (1.6-10.4) | |
| ≤ 10 pg/ml | 12 (40%) | 12 (80%) | 8 (80%) | 2 (66.7%) | |
| > 10-20 pg/ml | 10 (33.3%) | 2 (13.3%) | 2 (20%) | 1 (33.3%) | |
| > 20 pg/ml | 8 (26.7%) | 1 (6.7%) | 0 | 0 | |
| Serum DHEAS (µg/dl), median (range) | 307.1 (29.6-1500) | 28.5 (16.2-367)* | 38.8 (2.5-203) | 22 (15-19) | |
| Elevated DHEAS> Upper limit of normal | 9/18 (50%) | 2/11 (18.2%) | 1/6 (16.7%) | 0/2 | |
| Low DHEAS < Lower limit of normal | 3/18 (16.7%) | 6/11 (54.5%) | 2/6 (33.3%) | 2/2 | |
| Maximum lesion size (cm), mean (± SD) | 13.3 (±4.2)' | 3.5 (±0.9)* | – | 3.8 (±1.2) | |
| Tumor size> 6 cm | 28/30 (93.3%) | 0/15 | – | – | |
| Tumor size> 4 cm | 29/30 (96.7) | 4/15 (26.7%) | – | – | |
| Metastasis/Local invasion | 16/5 | 0/0 | – | – | |
| Tumor side (Right/Left) | 11/19 | 10/5 | – | – | |
| hyperplasia n = 3 bilateral macronodular | Dehydroepiandros- | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| DHEAS: | ||||||||||
| test; | ||||||||||
| adrenal Primary | ||||||||||
| – | – | – | – | – | – | – | – | |||
| suppression | ||||||||||
| n= 10 nodular | ||||||||||
| adrenal hyperplasia Primary pigmented | Overnight dexamethasone | |||||||||
| – | – | – | – | – | – | – | – | ODST: | ||
| adenoma | (%); | |||||||||
| (n=11) | n/N tomography. | |||||||||
| as | ||||||||||
| Adrenocortical n= 15 | (n=3) | described | ||||||||
| 1/11 | 7/11 | |||||||||
| (± 10.8)* | ||||||||||
| 66.5±17.9* | (n=1) | |||||||||
| 49.5±17.8*(n=11) | 8/11 | 6.2±1.8* | are emission | |||||||
| 23 | 1.9 | |||||||||
| specified (FDG)-positron | ||||||||||
| carcinoma | not | |||||||||
| are | ||||||||||
| (n=18) | units | |||||||||
| (n=18) | ||||||||||
| (n=10) | where | |||||||||
| Adrenocortical n=30 | 39.8 (±6)' | 0/18 | 42 ±23.8* | 16.7±11.3*(n=18) | 5/18 | 0/18 | 12.9±4.8* | 6.5±2.6 | Variables, Fluorodeoxyglucose | |
| PET) | PET: | |||||||||
| ACC and ACA cohorts. uptake value; FDG | ||||||||||
| SD) | (FDG | between standardized | ||||||||
| (± | ||||||||||
| mean | HU | ratio | ||||||||
| (HU), | <10 | SUVmean | difference Highest | |||||||
| Table 1 continued | density | density | Absolute washout (%) | Relative washout (%) | Absolute washout >60% | Relative washout> 40% | (FDG PET) | to liver | significant SUVmax: | |
| Unenhanced CT | Unenhanced CT | Lesion SUVmax | Lesion SUVmax | |||||||
| *Statistically terone sulfate; |
The younger age of our ACC cohort may represent the earlier age at presentation of cortisol-secreting ones, as also reported in a previous Indian study [16], than unselected ACC cohorts. Despite cortisol hypersecretion in all, clinical features of CS were present in only 46.7% of patients. This observation suggests considering a biochemical evaluation for CS in all ACC patients, irrespective of the clinical features. The majority (86.7%) of patients in our cohort had presented with abdominal symptoms, possibly due to delay in seeking healthcare or inefficient cortisol secretion or action (masked by the anabolic action of androgens). In addition, 53.3 % of patients had distant metastases at presentation, compared to lower metastasis rates (25 to 47.4%) in larger studies [3, 17]. This could reflect either delayed diagnosis or more aggressive nature of the disease in cortisol-secreting ACC. Corresponding with the pres- entation, the median survival in our cohort was also shorter than reported cohorts [17, 18].
The ACA subgroup in our study had a mean age of 25.7 ± 10.5 years, and predominant presentation due to overt CS in 80 % of pa- tients, which could be due to selection bias as patients with possi- ble autonomous cortisol production (ODS cortisol 1.8 to 5 µg/dl) were not included in the cohort. In addition, we had two pediatric patients who presented with co-secretion of sex steroids. Co-se- cretion of cortisol with sex steroids by ACA is rarely described and should raise the suspicion for malignancy [3, 19, 20]. Both of these patients had a Weiss score of 3 on histopathological examination and were disease-free at the last follow-up (5 and 5.5 years). How- ever, low-grade ACC cannot be ruled out in both these patients and are under close surveillance for recurrence of the disease. The mean duration for recovery of the HPA axis after surgery in our cohort was similar to the reported 11.2 months in literature [21].
In general, 71 % of benign adrenal masses have a basal HU of < 10 (lipid-rich) [22]. In contrast, only 9.1 % of cortisol secreting adeno- ma were lipid-rich in our study. Similar observations were made in two studies from France, one reporting 12% (3/25) and another re- porting 20.6% (7/34) of cortisol-secreting ACA having a basal HU of< 10 [23,24]. In a clinicopathological correlation study, unlike al- dosterone-secreting ACA that were characterized by lipid-rich clear cells, most of cortisol-secreting ACA were characterized by the presence of granule cells [25]. Similarly, in another study from France, lipid-poor (baseline attenuation:> 10 HU) cortisol-secret- ing ACA had <25% lipid-rich clear cells in 50 % [24]. In this study, the magnitude of cortisol hypersecretion in cortisol-secreting ACA was associated with lipid-poor nature, both on histopathology (<25% clear cells) and radiology (baseline HU). Hyperfunctioning nature with depletion of intracytoplasmic lipid droplets containing cholesterol esters necessary for cortisol synthesis or upregulation of cAMP pathway with a change from lipid-rich clear cell to li- pid-poor compact cell have been hypothesized to account for the lipid poor nature of cortisol-secreting ACA. Hence, basal attenua- tion of < 10 HU has less diagnostic sensitivity for cortisol secreting ACA. However, a baseline attenuation of < 10 HU excludes ACC, ir- respective of secretory status, and can be useful to differentiate ACA, including a small proportion of cortisol-secreting ones, with this radiological characteristic (10-20%) from ACC [23, 24, 26].
Size of the tumor>6 cm was 100% specific for the diagnosis of ACC, but sensitivity was 93.3 % (28/30). Poor relative contrast wash- out (<40%) was 100% sensitive for the diagnosis of ACC, but spec-
60
Discriminatory signs of CS
Absent
50
Present
Lowest ACTH (pg/ml)
40
30
20
10
0
ACC
Adenoma n=15
AIMAH
PPNAD n=10
n=30
n=3
| Patient No | Age/sex | Presentation | Discriminatory signs of CS | 8 AM serum cortisol (µg/dl) | ODST Serum Cortisol (µg/dl) | Plasma ACTH pg/ml (Assay platform) | Tumor size (cm) | Final diagnosis |
|---|---|---|---|---|---|---|---|---|
| P 1 | 45/F | Abdominal mass | No | 20.3 | 7 | 35.2 (SI) | 12 | ACC |
| P 2 | 40/F | Abdominal mass | No | 17.9 | 17.8 | 26.1 (SI) | 11.6 | ACC |
| P 3 | 46/M | Abdominal mass | No | 11.3 | 11.8 | 25.4 (SI) | 10.6 | ACC |
| P 4 | 30/M | Abdominal mass | No | 10.8 | 8.4 | 46 (SI) | 19 | ACC |
| P 5 | 45/M | Abdominal mass | No | – | 9 | 27.7 (SI) | 18.9 | ACC |
| P 6 | 45/F | Abdominal mass | Yes | 19.3 | 25.1 | 27.9 ,(SI) | 13 | ACC |
| P 7 | 29/F | Abdominal mass | Yes | – | _a | 52.9 (SI) | 10 | ACC |
| P 8 | 42/M | Abdominal mass | Yes | 32.8 | _a | 37.5 (SI) | 8.9 | ACC |
| P 9 | 21/F | Cushing's syndrome | Yes | 28.5 | 28 | 49.6 (SI) | 3.2 | ACA |
a Urinary free cortisol was 1.7 and 7.3 times the upper limit of normal for P7 and P8, respectively; F: Female, M: Male; ACC: Adrenocortical carcinoma; ACA: Adrenocortical adenoma; ODST: Overnight dexamethasone suppression test; SI: Siemens Immulite.
ificity was 72.7%, as few [3/11 (27.3%)] ACA exhibited poor wash- out. This is in concordance with data in general, where lipid-poor adenoma has poor washout in 41 % of the patients [27]. Hence, a role FDG-PET/CT has been suggested by He et al. to differentiate the malignant lesions (higher SUVmax and higher lesion SUVmax to liver SUVmean ratio) from benign ones [28]. Similar values of these two parameters were noted in our study too. Notably, a pa- tient with ACC had a lesion size of <6 cm, but the lesion SUVmax of 11.6 was suggestive of malignancy. Similarly, a patient of ACA with poor washout characteristics had a lesion SUVmax of 6.7, which was indicative of its benign nature. Also, higher FDG uptake has been observed in cortisol-secreting ACA in comparison to non-se- creting ones [23].
PBMAH patients of our study presented later in life either with subclinical (n=2) or clinical CS (n = 1), which is similar to the avail- able literature. Unlike ACC, ACTH was suppressed in all three pa- tients despite subclinical CS in two patients. The decision for bilat- eral adrenalectomy or medical management was individualized based on the clinical severity of hypercortisolemia and comorbid- ities, as suggested previously [4].
We report that plasma ACTH of > 20 pg/ml is not uncommon in patients with adrenal CS, especially in ACC. In contrast, unsup- pressed ACTH in adrenal CS is limited to a few cases in the litera- ture. Adrenal CS cases reported in the literature (ODST serum cor- tisol value >5 µg/dl and/or 24-hour UFC more than the upper limit of normal) with unsuppressed ACTH are summarized in >> Table 3. Unsuppressed ACTH in adrenal CS may prompt unnecessary inves-
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100
80
Survival probability (%)
60
40
20
0
0
10
20
30
40
50
60
70
80
Number at risk 29
Duration since diagnosis (months)
16
12
8
4
1
1
1
0
tigations like MRI pituitary, IPSS, CT thorax and neck, and/or nucle- ar scans, and in unfortunate instances, even an unnecessary pitui- tary surgery [7-9]. Unsuppressed ACTH has been reported mostly with ACA, whereas in our series, we observed eight patients of ACC had plasma ACTH> 20 pg/ml. The varying postulates for such high ACTH values can be assay-related concerns, aberrant precursors secreted by the tumor, or intra-adrenal ACTH production.
Assay-related concerns leading to high ACTH can be attributed to the type of ACTH assay, different ACTH platforms, or heterophile antibody interference [8, 9, 29-32]. Traditionally, radioimmu- noassays (RIA) were used, which also measure clinically insignifi- cant fragments of POMC-ACTH and caused spurious elevations of ACTH. Immunoradiometric (IRMA) assays have improved this draw- back as the “sandwich” complexes ensure specificity. As observed in an Italian multicentric study, plasma ACTH of > 20 was observed in four patients of adrenal CS by RIA, as against a single case by IRMA [33]. Contemporary chemiluminescence sandwich immuno- assay platforms use different capture and detection antibodies, and this can lead to a difference in ACTH measured, especially at lower ACTH levels, as shown by a study from Italy [34]. In a recent study, plasma intact ACTH level measured by LC-MS/MS highly positively correlated with plasma ACTH measured by Roche but not with that by Siemens; also, among the three discordant samples in which plasma ACTH by LC-MS/MS was undetectable, that by Roche was <20 pg/ml in two but was more than 100 pg/ml in all when measured by Siemens [35]. As depicted in > Table 3, in many cases, the ACTH detected by Siemens Immulite was much greater than Roche Elecsys performed subsequently. Similarly, all patients with ACTH of>20 pg/ml in our series were measured on the Siemens Immulite platform. Although a repeat ACTH estimation was not available for these patients, that by Liaison assay in another five pa-
tients with an initial ACTH of 13 pg/ml by Siemens Immulite assay was suppressed (<13 pg/ml) in all (> Table 3) suggesting a major role for assay-related issues in an apparently unsuppressed ACTH. Notably, most (8/9) of our patients with this phenomenon had ACC that makes us think of an additional role for ACC-related, yet-uni- dentified, factors in causing a plasma ACTH of> 20 pg/ml. As con- ceptualized in an old study, steroidogenic precursors (21-deoxy- cortisol) secreted by ACC may antagonize the glucocorticoid feed- back at the hypothalmic-pituitary level [36, 37]. Although the intra-adrenal source of ACTH has been reported in PBMAH and mixed cortico-medullary adrenal tumors (MCMT), the evidence to support the production of ACTH or ACTH-like substances from ACC is negligible [38, 39]. The evaluation for the possible role of heter- ophile antibodies was not performed in our study.
Hence, when ACTH is measured by the Immulite assay and is>20 pg/ml in an endogenous CS patient, one must be cautious and rule out ACC especially in the presence of clinical or biochem- ical evidence of androgen excess and/or local abdominal mass ef- fects, before ordering MRI pituitary. Repeating ACTH on a different platform using a more accurate ACTH assay and even considering adrenal imaging if clinical suspicion is high may help in correct di- agnosis.
Our study is a retrospective analysis with inherent limitations. Serum DHEAS was not available in some patients. The lack of LC-MS/MS steroid profile and ACTH measurements from different platforms are other limitations. Nonetheless, all the included pa- tients had confirmed adrenal CS with a significant sample size, and detailed clinical, biochemical and radiological features along with clinical outcomes are described.
To conclude, adrenal CS has a varied spectrum of clinical, bio- chemical, and imaging features that may help to differentiate ma- lignant causes from benign ones. Cortisol-secreting ACA is usually
| No. [Ref] | Age (years)/Sex (M/F) | Discriminatory signs of CS | Presentation | Tumor size (cm) | ODST (µg/dl)/UFC (pg/day or times x ULN) | Plasma ACTH pg/ml (Assay platform) | Revised Plasma ACTH pg/ml (Assay platform) | Investigation done for localizing the site of excess ACTH | Final diagnosis |
|---|---|---|---|---|---|---|---|---|---|
| 1 [8] | 43/F | Yes | CS | 3 | -/- | 56 (SI) | <1 (RE) | MRI pituitary Indium111 Pentreotide scan, FDG PET CT, Chest CT | ACA |
| 2 [8] | 48/F | No | Incidentaloma | 3.8 | -/>ULN | 19 (SI) | 1.76 (RE) | – | ACA |
| 3 [8] | 26/F | Yes | NA | 4.2 | -/>ULN | 98.5 (SI) | < 5 (RE) | – | ACA |
| 4 [8] | 46/F | Yes | NA | 3.3 | -/>ULN | 14 (SI) | <1 (RE) | MRI pituitary, IPSS | ACA |
| 5 [9] | 30/F | Yes | CS | 2.5 | 20.6/537 | 62 (SI) | 2.4 (T) | MRI pituitary, Gallium-68 DOTATATE scan × 2, IJVS, IPSS | ACA |
| 6 [9] | 55/F | Yes | CS | 2.1 | 26.7/132 | 143 (SI) | 3.9 (T) | MRI pituitary, MIBG scan, Gallium-68 DOTATATE scan, IJVS, IPSS | ACA |
| 7 [9] | 23/F | Yes | CS | 2.5 | 14.4/127 | 21 (SI) | 1 (R) | MRI pituitary | ACA |
| 8 [7] | 25/M | Yes | CS | 11.7 | 24.28/- | 15.8ª | < 1ª | Pituitary surgery | ACC |
| 9 [30] | 44/F | No | NA | 2.5 | 13.4/- | 23.16 (SI) | < 10 (PEG, SI) | – | PBMAH |
| 10 [30] | 69/F | No | NA | 2.7 | 6.6/- | 22.25 (SI) | <5 (HBT, SI) | IPSS | ACA |
| 11 [30] | 28/F | Yes | CS | 3.3 | 18.7/- | 54.95 (SI) | < 10 (PEG, SI) | Gallium-68 DOTATATE scan, FDG PET/CT IPSS | ACA |
| 12 [31] | 60/F | No | Incidentaloma | 2.3 | 20.3/2.3 ×ULN | 16 (SI) | < 0.05 (RE) | IPSS | PBMAH |
| 13 [32] | 54/M | Yes | NA | 3.2 | -/4 ×ULN | 65.39 (SI) | 0.9 (RE) | IPSS | ACA |
| Patients from this study | |||||||||
| 1 | 1/F | Yes | CS | 3.9 | 9.01/- | 149 (SI) | 5.8 (LD) | – | ACC |
| 2 | 37/F | Yes | CS | 3 | 21.4/- | 44.2 (SI) | 1.6 (LD) | – | ACA |
| 3 | 30/F | Yes | CS | 3.6 | 37.2/- | 36 (SI) | 12.7 (LD) | – | ACA |
| 4 | 26/M | Yes | CS | – | 22.8/1500 | 13.7 (SI) | 2.55 (LD) | – | PPNAD |
| 5 | 30/F | Yes | CS | 3.4 | 25.4/- | 13.1 (SI) | 1.6 (LD) | – | PBMAH |
NA: Details not available; ULN: Upper limit of normal; SI: Siemens Immulite assay; RE: Roche Elecsys assay; T: Tosoh AIA assay; R: Roche Cobas assay; LD: Liaison DIasorin assay; FDG PET: Fluorodeoxyglucose (FDG)-positron emission tomography; IPSS: Inferior petrosal sinus sampling; IJVS: Internal jugular vein sampling; MIBG: Meta-iodobenzylguanidine; ACA: Adrenocortical adenoma; ACC: Adrenocortical carcinoma; PBMAH: Primary bilateral macronodular adrenal hyperplasia; ª Assay details not available.
lipid-poor, and baseline HU is not a sensitive radiological parame- ter to distinguish cortisol-secreting ACA from ACC. Plasma ACTH levels may be> 20 pg/ml in adrenal CS when measured by Siemens Immulite assay, especially in patients with ACC, which can be ad- dressed by using more accurate ACTH assays.
Data Availability Statement
The data that support the findings of this study are available on re- quest from the corresponding author. The data is not publicly avail- able due to privacy or ethical restrictions.
Conflict of Interest
The authors declare that they have no conflict of interest.
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