Role of adrenal venous sampling in the differential diagnosis of ACTH-independent Cushing’s syndrome with bilateral adrenal mass

doi:10.21203/rs.3.rs-2366602/v1

Purpose: The diagnosis and management of corticotropin-independent Cushing’s syndrome (AICS) with bilateral adrenal mass remain challenging. Some studies have explored the value of adrenal vein sampling (AVS) in patients with AICS; however, more investigations are needed to assess its benefits for diagnosis and treatment planning in this population.

Methods: Ten patients with imaging and biochemical evidence of AICS received AVS at our institution from 2017-2021, and their data, including demographics, laboratory results, adrenal mass and clinical characteristics, were analyzed. Serum cortisol and plasma aldosterone concentrations of the adrenal vein and inferior vena cava were measured. AVS-guided adrenalectomy was performed. Histology and immunohistochemistry of the adrenal tissues were analyzed. The prognosis was evaluated based on symptomatic improvement, serum cortisol normalization or both.

Results: Bilateral adrenal mass were noted via computed tomography imaging in ten patients. The mean (± SD) maximal diameter of the adrenal mass was 1.84±0.93 cm (0.4-3.4 cm). Blood samples were successfully collected from both adrenal veins and inferior vena cava in seven patients, with lateralization index values ranging from 1.00-3.38. Blood from the right adrenal vein was not collected in three patients; instead of the lateralization index, their left adrenal vein to inferior vena cava cortisol gradient was analyzed. The AVS and postoperative pathological results were consistent. During the mean follow-up of 45.7 months, all ten patients achieved clinical improvement.

Conclusion: Our study suggested that AVS helps distinguish unilateral disease from bilateral disease and localize autonomous hypercortisolism glands, thereby improving therapeutic strategy selection for patients with AICS and bilateral adrenal mass.

Adrenal vein sampling (AVS)

ACTH-independent Cushing’s syndrome (AICS)

Bilateral adrenal mass

primary bilateral macronodular adrenal hyperplasia (PBMAH)

Primary pigmented nodular adrenocortical disease (PPNAD)

Adrenocorticotropic hormone-independent Cushing’s Syndrome (AICS), which is caused by adrenal mass and is known as adrenal CS, accounts for approximately 20% of endogenous CS and is characterized by autonomous cortisol production with a suppressed plasma adrenocorticotropic hormone (ACTH) concentration. The diagnosis of AICS is mainly based on loss of circadian rhythm of cortisol regulation and inhibition of ACTH. Most of the adrenal mass of AICS are unilateral cortisol-secreting adenomas seen via computed tomography (CT) scanning¹, leading to straightforward treatment by adenoma resection. However, cases of AICS with bilateral adrenal mass are emerging in clinical practice, accounting for approximately 10% of AICS cases², and should be treated with caution.

According to the literature, patients with AICS and bilateral adrenal mass may present with unilateral cortisol-secreting adenoma with a contralateral nonfunctional nodule (UAA), bilateral functional adrenal adenomas (BAA, accounting for < 2% of CS cases), primary bilateral macronodular adrenal hyperplasia (PBMAH, accounting for approximately 2% of CS cases)³ or primary pigmented nodular adrenocortical disease (PPNAD, accounting for 10% of AICS cases)²pretending as bilateral single adenoma. On the grounds that different subtypes of AICS require different management strategies, it is important to accurately diagnose and plan the proper therapy strategy for the disease.

Nevertheless, to date, it is still challenging to diagnose AICS with bilateral adrenal mass. Although CT and MRI play important roles in indicating tumor location, they cannot identify hypersecretory mass. Adrenal venous sampling (AVS), which is recommended as the most accurate method to locate the source of aldosterone hypersecretion in primary aldosteronism, has been reported to be useful in subtyping AICS and bilateral adrenal mass^{4, 5}. However, the diagnostic value of AVS in bilateral adrenal mass has been reported in only a few case reports. More studies are needed to standardize the application of AVS in this context of adrenal mass.

We herein report our experience with applying AVS to the diagnosis and treatment planning of patients with AICS and bilateral adrenal mass. Our study aimed to further explore the value of AVS in such patients.

Subjects and assays

This was a retrospective analysis of ten patients with AICS who received AVS at our institution between 2017 and 2021. All patients were initially evaluated clinically and biochemically. The plasma aldosterone concentration (PAC), plasma ACTH concentration at 8 a.m., serum cortisol concentration at 8 a.m. (PTC 8:00) and midnight (PTC 24:00), and 24 h urine free cortisol (UFC) were measured, and an overnight 1 mg dexamethasone suppression test (DST) was performed. The diagnostic criteria included at least two of the following results: (a) loss of circadian rhythm of cortisol regulation, (b) 24 UFC above the upper limit of normal (20.26-127.55 nmol/L), and (c) PTC level higher than 140 nmol post DST plus suppressed plasma ACTH concentration (<10.0 ng/L).

Written informed consent was obtained from each patient after full explanation of the purpose and nature of all procedures used before the study participation. The study protocol was reviewed and approved by the Ethics Committee of West China Hospital. The study protocol conformed to the principles of the Declaration of Helsinki.

AVS technique

The AVS protocol (without cosyntropin use) was uniform for all ten patients⁶. Blood samples were obtained sequentially from the inferior vena cava (IVC) and both adrenal veins (AV) to measure PTC and PAC. An AV to IVC aldosterone ratio (selectivity index, SI) over 2 confirmed successful sampling. The PTC to PAC ratio (PTC/PAC) was compared between AVs, and the high-side to low-side PTC/PAC ratio was calculated as the lateralization index (LI). An LI over 2 was interpreted as unilateral disease.

Histology and immunohistochemistry

Hematoxylin and eosin (HE) staining of the adrenal tissues was performed by two pathologists who were blinded to the experiments. Four fields in each section and four sections per person were observed and quantified. Immunohistochemistry was performed according to the standard histopathological protocol described in a previous study⁷. Based on the differential expression of two subtypes of 11-hydroxylase (CYP11B1⁸ and CYP11B2⁹) in distinguishing aldosterone-producing adenoma and cortisol-producing adenoma, we applied immunostaining for CYP11B1 (rat monoclonal, 1:200; Merck Millipore, MABS502, RRID: AB_2650563) and CYP11B2 (mouse monoclonal, 1:200; Merck Millipore, MABS1251, RRID: AB_2650562) to help verify the differential diagnosis of AICS. A standard avidin-biotin-peroxidase complex technique was used to demonstrate primary antibody binding (Vector pk-7200; Vector Laboratories, Inc., Burlingame, CA, United States).

Statistical analysis

Continuous variables are presented as the mean ± SD or median (range). Categorical data are summarized as frequencies and percentages. Statistical analysis was performed using GraphPad Prism 8.2 software (GraphPad, San Diego CA), with p<0.05 considered statistically significant.

Participants

We carried out a retrospective review and regular follow-up of ten patients hospitalized in our institute from February 2017 to July 2021, including seven females and three males aged from 15 to 55 years (40.30±13.69 years). Each patient presented with at least 3 typical clinical symptoms or signs of CS, including moon face, central obesity, buffalo hump, acne, hirsutism, purple striae, easy bruising, edema and proximal myopathy (Table 1). More than half of the patients developed moon face, central obesity, buffalo hump and purple striae. Six of the ten patients were obviously obese, with an average BMI of 25.07±2.92 kg/m². The mean waist circumference (WC) of seven patients with successful AVS was 90.78±10.81 cm before surgery. In addition, all patients underwent clinical and biochemical evaluations (Table S1).

Table 1. Physical examination of the ten patients

Case No.	Age	sex	Hight (m)	Weight (Kg)	BMI (Kg/m²)	AC (cm)	BP (mmHg)	moon face	central obesity	buffalo hump	acne	hirsutism	purple striae	easily bruising	edema	Proximal myopathy
1.1*	55	F	1.56	54.0	22.19	-	164/101	+	+	+	-	-	-	+	+	-
1.2*	57	F	1.56	49.0	20.13	84	-	-	-	-	-	-	-	-	-	-
2	42	F	1.54	55.0	23.19	95	180/120	+	+	+	-	-	+	+	+	-
3	42	F	1.50	63.5	28.22	-	Normal	+	+	-	-	-	-	-	-	+
4	54	M	1.70	67.5	23.36	93.5	200+/120		+	-	-	-	-	-	+	-
5.1*	31	F	1.63	82.6	31.10	112	170/110	+	+	+	+	+	+	-	-	-
5.2*	31	F	1.63	74.0	27.85	107	133/88	+	+	+	+	-	+	-	-	-
6	46	F	1.47	53.0	24.53	88	158/99	+	+	-	-	-	+	+	+	-
7	46	F	1.51	55.5	24.34	-	180/120	+	-	+	-	-	-	-	+	+
8	51	M	1.70	79.5	27.50	-	-	-	-	-	-	-	-	-	-	-
9	21	F	1.56	54.0	22.19	81	159/108	+	+	-	+	+	+	-	-	-
10	15	M	1.41	48	24.14	82	141/105	+	-	-	-	-	-	-	-	-

*1.1 case 1 before the first surgery; 5.1 case 5 before the first surgery;1.2 case 1 before the second surgery; 5.2 case 5 before the second surgery; BMI body mass index; BP blood pressure; AC abdominal circumference; - non.

The tests mentioned above related to the evaluation of cortisol hypersecretion are described in Table 2. Plasma catecholamine concentrations, renin activity, angiotensin and PAC were measured to exclude pheochromocytoma and primary aldosteronism. All patients met the diagnostic criteria of AICS. Case 4 revealed that he had both cortisol and aldosterone autonomous secretion simultaneously.

Table 2. Clinical characteristics of the ten patients

Case	Diurnal rhythm cortisol					DST
No.	PTC(8:00)	PTC(16:00)	PTC(24:00)	24hUFC	ACTH	PTC
	(133-537nmol/L)			(20.3-127.6ug）	(5-78ng/L)	(nmol/L)
1.1*	858.4	669.5	716	634.8	＜1.00	787.5
1.2*	249.67	-	207.4	73	＜1.00	-
2	322.1	294.6	245	126.8	1.61	311
3	487.3	226.3	359.1	134.5	7.18
4	738.5	674.6	681.4	768.6	1.21	720.3
5.1*	671.3	709.3	646.4	941.7	1.6	781.8
5.2*	181.9	199.4	191.4	152.3	2.06	200.7
6	799.7	-	723.8	886.5	1.78	-
7	440.3	435.5	376.2	968.3	＜1.00	596.1
8	242.6	300.8	224.9	81.5	3.11
9	452.7	-	407.2	764.9	＜1.00	464
10	690.76	593.34	551.78	521.1	2.25	677.09

*1.1 case 1 before the first surgery; 5.1 case 5 before the first surgery;1.2 case 1 before the second surgery; 5.2 case 5 before the second surgery; - not available; PTC plasma total cortisol; ACTH adrenocorticotropic hormone; 24h UFC 24h urine free cortisol; DST dexamethasone-suppression tests.

All patients received CT scans and showed bilateral adrenal mass (Table 3 and Figure 1). Five cases (cases 1, 2, 3, 5, and 7) manifested bilateral solitary nodules surrounded by atrophic adrenal tissue, four cases (cases 6, 8, 9, and 10) presented massively enlarged adrenal glands bilaterally with numerous nodules, and one case (case 4) had unilateral solitary nodule with contralateral adrenal hyperplasia. The mean maximal diameter of these masses was 1.84±0.93 cm. The mean Hounsfield units of the adrenal masses were 16.23±10.86 on unenhanced and 89.23±26.56 on enhanced images.

Table 3. Patient’s CT findings

Case No.	Size（cm）		CT-Right		CT-Left		Description of CT finding	Suggestion
Case No.	Right	Left	HU-unenhanced	HU-enhanced	HU-unenhanced	HU-enhanced	Description of CT finding	Suggestion
1	2.8	2.1, 0.6	30	88	19	95	Right: solitary round nodule; Left: 2 nodules, uniform density, smooth edges, inhomogeneous enhanced, with normal adrenal atrophy	Bilateral adenoma
2	2.0	2.6	4	75	4	64	Bilateral solitary round soft tissue density nodule, smooth edges, obviously enhanced, with normal adrenal atrophy	Bilateral adenoma
3	1.3	1.6	33	140	22	140	Bilateral solitary round soft tissue density nodule, uniform density, smooth edges, inhomogeneous enhanced, with normal adrenal atrophy	Bilateral adenoma
4	3.4	*	-1	58	NA	NA	Right: solitary low density round nodule, uneven enhanced. Left: hyperplasia, homogeneous enhancement	Right adenoma+ Left hyperplasia
5	2.3	2.6	NA	NA	NA	NA	Bilateral solitary round soft tissue density nodules, smooth edges, obviously enhanced, with normal adrenal atrophy	Bilateral adenoma
6	1.3	1.6	26	101	26	98	Bilateral irregular hyperplasia, local nodular, mild enhanced	Hyperplasia
7	1.0	3.1	7	57	11	79	Bilateral solitary round nodule, rules of form, clear edge, enhanced obviously	Bilateral lesions
8	2.1	2.7	13	80	16	85	Bilateral diffuse nodular hyperplasia	Hyperplasia
9	*	Thickening	NA	NA	NA	NA	Bilateral diffuse hyperplasia	Hyperplasia
10	0.4	*	18	84	NA	NA	Right: solitary round nodule; Left: diffuse hyperplasia	Bilateral lesions

HU hounsfield units, NA not available, * hyperplasia.

The treatment of CS¹⁰ was recommended to normalize cortisol concentrations, eliminate the signs and symptoms of CS and treat comorbidities associated with hypercortisolism. Approaches to remove the mass were recommended; for instance, unilateral adrenal resection was suggested for cases of benign unilateral disease. AVS was performed in all ten cases, and treatment was planned according to the results (Table 4). The diagnosis and management of the ten patients are shown in Figure 2.

Table 4. Results of adrenal venous sampling

Case No.	Mean PTC (nmol/L)			PTC		Mean PAC (nmol/L)			PAC		PTC/ PAC ratio		LR	LI	Interpretation (Side of hypercortisolism)
	Mean PTC (nmol/L)			(AV:IVC)		Mean PAC (nmol/L)			(AV:IVC)		PTC/ PAC ratio
	IVC	R-AV	L-AV	Right	Left	IVC	R-AV	L-AV	Right	Left	R-AV	L-AV
1	438.45	8836.50	8524.67	20.15	19.44	6.16	31.70	25.88	5.15	4.20	278.75	329.39	(L:R)1.18	(R:L) 1.04	Bilateral
2	655.45	15162.33	7999.00	23.13	12.20	17.19	76.05	55.84	4.42	3.25	199.37	143.25	(R:L)1.39	(R:L) 1.90	Bilateral
3	330.95	412.40	5258.25	1.25	15.89	14.05	10.31	58.03	0.73	4.13	40.00	90.62	(L:R)2.27	(L:R) 12.75	Left
5	625.60	6781.07	6191.20	10.84	9.90	21.23	49.91	47.11	2.35	2.22	135.87	131.42	(R:L)1.03	(R:L) 1.10	Bilateral
6	801.00	11738.00	3472.33	14.65	4.33	15.65	55.64	40.82	3.56	2.61	210.98	85.06	(R:L)2.48	(R:L) 3.38	Right
7	423.85	428.60	2205.00	1.01	5.20	11.76	8.15	50.46	0.69	4.29	52.59	43.70	(R:L)1.20	(L:R)5.14	Left
8	355.30	350.70	1818.25	0.99	5.12	17.65	22.09	58.10	1.25	3.29	15.87	31.29	(L:R)1.97	(L:R) 5.18	Left
9	485.00	17824.33	15717.00	36.75	32.41	14.40	68.13	73.84	4.73	5.13	261.62	212.85	(R:L)1.23	(R:L) 1.13	Bilateral
10	571.00	15608.00	16453.00	27.33	28.81	3.21	13.6	14.3	4.24	4.45	1147.64	1150.56	(L:R)1.05	(L:R)1.00	Bilateral

Mean PTC (nmol/L)

PTC

Mean 17-αOH (nmol/L)

17-αOH

PTC/17-αOH ratio

LR

LI

Interpretation

(AV:IVC)

IVC

R- AV

L-AV

Right

Left

IVC

R-AV

L-AV

Right

Left

R-AV

L-AV

4

493.85

3561.50

780.48

7.21

1.58

1.82

17.71

9.25

9.73

5.08

201.1

84.38

(R:L)2.38

(R:L)4.56

Right

Mean PAC (nmol/L)

PAC

Mean 17-αOH (nmol/L)

17-αOH

PAC/17-αOH ratio

LR

LI

Interpretation

(AV:IVC)

IVC

R-AV

L-AV

Right

Left

IVC

R-AV

L-AV

Right

Left

R-AV

L-AV

PTC serum cortisol, PAC plasma aldosterone concentration, AV adrenal vein, IVC Inferior vena cava, LR lateralization ratio, LI lateralization index, R right, L left.

Management of patients with successful AVS

Cases 1, 2 and 5 were clinically diagnosed as BAA. The SI values were over 2, which indicated successful sampling of AVS. The LI values of the three cases were under 2.0 (1.04, 1.90, and 1.10, respectively), which indicated bilateral autonomous cortisol hypersecretion without a predominant side. Bilateral adenoma resection was considered a reasonable option for the three cases. In detail, cases 1 and 5 underwent stepwise bilateral adenoma resection considering their poor cardiac function. Case 2 underwent bilateral adrenal adenoma resection simultaneously and was advised to receive hydrocortisone. The postoperative immunohistochemical examination of the resected tissues (taking case 5 as an example) showed relatively high CYP11B1 expression but no CYP11B2 expression (Figure 3).

For case 4, who was considered to have cohypersecretion of cortisol and aldosterone, we defined the AV to IVC 17-α-hydroxy progesterone (17α-OH-P) gradient ≥2 as successful sampling. Both the PTC to 17α-OH-P ratio and PAC to 17α-OH-P ratio were over 2 (right to left: 4.56 and 8.91, respectively), which suggested right hypersecretion and resulted in right adrenal adenoma resection. The postoperative immunohistochemical analysis (Figure 4) showed coexpression of CYP11B1 and CYP11B2, which verified the diagnosis of right adrenal aldosterone and cortisol cosecreting adenoma.

Management of patients with failed AVS

Three patients (cases 3, 7 and 8) failed to have blood collected from the right AV with right SI values of 0.73, 0.69, and 1.25, respectively; thus, instead of LI, the left AV to IVC cortisol gradient was analyzed, which was 15.89, 5.20 and 5.12, respectively. Considering that an AV to IVC cortisol gradient (PTC AV:IVC) between 4.1-6.4 was indicative of adrenal hyperplasia with cortisol hypersecretion, and a value over 6.5 indicated cortisol-secreting adrenal adenoma^{4, 11}, our AVS results suggested that case 3 had left adrenal adenoma and cases 7 and 8 had left adrenal hyperplasia. Furthermore, CT scanning showed that both case 3 and case 7 had a larger nodule on the left adrenal gland. Considering their clinical characteristics, AVS results and CT findings, left adrenalectomy was performed for the three cases. The pathological analysis of the adrenal tissues verified BAA in case 3 and PBMAH in cases 7 and 8 (Figure 6, taking case 7 as an example).

Follow-up and further treatments

Patients were followed up for 1 to 5 years for clinical signs and biochemical tests (Figure 7) after the operation. Remission of the clinical symptoms was achieved in most of these patients, including pathological signs, body weight, and blood pressure.

Patients with successful AVS

The symptoms and signs of cases 1 and 5 were significantly alleviated 3 months after unilateral adrenal adenoma resection. Cases 1 and 5 had reductions in body weight by 5 kg and 4.6 kg and in WC by 4 cm and 5 cm, respectively. However, both cases retained an absence of a diurnal rhythm of serum cortisol and low ACTH concentration, suggesting autonomous cortisol secretion from the contralateral adrenal gland. Consequently, 3 months after the first surgery, right adrenal adenoma resection was performed for case 1, and left adrenal adenoma resection was chosen for case 5. Both patients received glucocorticoid supplementation immediately after the second operation and were recommended lifetime administration. Case 1 lost 9 kg of weight, and the WC decreased to 71 cm (88 cm at the first visit) 13 months after the later surgery. Regarding case 5, she discontinued glucocorticoid supplementation privately at 1.5 years after the second surgery. Fortunately, she did not experience poor quality of life, although her ACTH and PTC concentrations dropped beyond the normal range during the past 5 years after bilateral adrenal adenoma resections.

Regarding case 2, her blood pressure became normal immediately after the operation. The clinical signs of CS gradually disappeared as the ACTH concentration increased from 1.08 to 95.24 ng/L and PTC to 166 to 277 nmol/L. Unfortunately, she still suffered from osteoporosis and received vitamin D supplements and anti-osteoporosis therapy during the 4-year follow-up period.

The most significant improvement in case 4 was blood pressure, which dropped sharply from over 200/120 mmHg to 130/85 mmHg and remained at approximately this level. Moreover, the serum potassium increased from 2.48 to 3.13 mmol/L. Other improvements also occurred, including the patient’s general condition and clinical signs, with an ACTH concentration rising from <1.00 ng/L to 2.50 ng/L 3 months after the right adrenalectomy and eventually returning to normal (73.78 ng/L), and PTC declining to normal (166.40 nmol/L) after 6 months. From then on, her ACTH concentration (72.59 ng/L) and PTC (483.90 to 644.50 nmol/L) were normal during the 4-year follow-up period.

Regarding case 6, her ACTH concentration was still under 1 ng/L, while her PTC was normal (467.2 nmol/L) 2 months after the operation. In addition, the concentrations of PTC continued to increase from 539.60 to 675.5 nmol/L, and ACTH concentrations ranged from 1.34 to 1.57 ng/L during a 1.5-year follow-up, which resulted in supplementary surgery 20 months after the first surgery, and she was recommended to receive glucocorticoid supplementation for the rest of her life. Her pathological diagnosis was PBMAH. Her general condition was good without obvious problems with glucose metabolism or blood pressure during the 3-year follow-up after the second surgery. The latest biochemical analysis showed that her PTC dropped from 675.5 to 4.71 nmol/L, but her ACTH increased from 1.34 to 76.91 ng/L.

After the first unilateral adrenalectomy operation, the PTC of case 9 returned to within a normal range (123.90 nmol/L), but the ACTH concentration was still suppressed (<1.00 ng/L), so contralateral adrenalectomy was performed 13 months later. Consequently, glucocorticoid supplementation was advised for the rest of her life. The clinical symptoms of CS improved greatly, and the ACTH concentration remained normal 4 years after surgery.

Regarding case 10, the most notable improvement after surgery was his height, which increased by 2.5 cm after 3 months, 6 cm after 6 months, and 12 cm after 16 months. His body weight decreased by 4 kg, and he presented with a thinner body shape; his blood pressure became normal without taking medicine after bilateral adrenalectomy. During the 1.5-year follow-up period, he was receiving glucocorticoid replacement therapy without any complaints and normal ACTH.

Patients with failed AVS

Regarding case 3, her general situation improved, and she did not complain of any problems with glucose metabolism or blood pressure, although her assay showed an ACTH concentration of 1.26 ng/L 13 months later and persistent suppression during the past 5 years. Both cases 7 and 8 had ameliorated symptoms combined with improved laboratory examinations compared with before the surgery. The PTC of case 7 dropped to 130.40 nmol/L 3 months after her unilateral adrenalectomy and remained in the normal range (the latest PTC was 212 nmol/L) during the past 4 years. However, her ACTH concentration remained suppressed at the latest level of 2.29 ng/L, and she is currently suffering from cardiovascular disorders and chronic kidney disease. Similarly, case 8 had a normal PTC ranging from 283.4 to 485.2 nmol/L and a persistently low ACTH concentration ranging from 2.53 to 3.32 ng/L 12 months after the surgery.

The etiological diagnosis and surgical options for patients with AICS and bilateral adrenal mass are difficult to perform. Although CT provides the location, size and shape of adrenal mass intuitively, which plays an indispensable role in clinical diagnosis, this modality is unable to distinguish functional cortisol-producing adenomas from nonfunctional ones, which results in dilemmas in selecting proper treatment. AVS may solve this problem, as our study demonstrated that AVS was helpful in determining the dominant side of AICS and guided a reasonable diagnosis and management of all ten patients.

Our study found that the dominant hypersecretion side suggested by AVS was consistent with the postoperative analysis of the adrenal lesion. Five patients had an LI less than 2, which indicated bilateral disease and was in line with the postoperative diagnosis of BAA. Case 4 had both a PTC to 17α-OH-P ratio and PAC to 17α-OH-P ratio over 2 (right to left), which suggested right adrenal aldosterone and cortisol cosecreting adenoma. The postoperative histology verified the diagnosis. Case 6 had an LI over 2, which indicated unilateral disease and a right adrenalectomy initially. However, we found that the left AV to IVC cortisol ratio of case 6 was 4.33, which suggested adrenal hyperplasia with cortisol hypersecretion of the left adrenal gland. Combining this result with the clinical symptoms and PTC after right adrenalectomy of case 6, we performed a left adrenalectomy for her 20 months later. In cases 3, 7 and 8, blood was not collected from the right AV, and the left AV to IVC cortisol gradients suggested adrenal adenoma of case 3 and hyperplasia of cases 7 and 8, which were consistent with the postoperative diagnoses of BAA for case 3 and PBMAH for cases 7 and 8.

Based on the important role of AVS for determining the dominant hyperaldosteronism side. Young et al from the Mayo Clinic ⁴ originally reported the application of AVS in AICS patients and recommended that 1) measurements of serum epinephrine concentrations are needed to confirm successful sampling, 2) an AV to IVC cortisol gradient between 4.1–6.4 was indicative of adrenal hyperplasia with cortisol hypersecretion, and a value over 6.5 indicated cortisol secreting adrenal adenoma, and 3) a side-to-side (high-side to low-side) AV cortisol lateralization ratio (LR) ≥ 2.3 was consistent with autonomous cortisol secretion from predominantly one adrenal mass, with an LR ≤ 2.0 indicating bilateral cortisol hypersecretion. Since then, this protocol has been used in more studies on AICS¹².

Considering that the operational process might act as a stress factor to induce adrenaline secretion, PAC might be a more stable parameter. We applied a ratio between the PAC in AV and IVC gradients ≥ 2 to confirm successful sampling. In addition, some studies suggested that an LR ≥ 2.3 was obviously defective and should be corrected by aldosterone^{5, 13}. We used a high-side to low-side AV PTC to PAC ratio (LI) ≥ 2 to define predominantly autonomous unilateral cortisol secretion. Additionally, notably, in case 4, hypercortisolism and hyperaldosteronism were detected simultaneously. In this situation, we used the serum 17-α-OH-P concentration instead of aldosterone as a reference for successful sampling and LR correction.

There is no consensus on a uniform principle or cutoff value of LI for AVS in the setting of AICS with bilateral adrenal mass. The mean LI of the seven successful AVS cases was 1.6, but more data are needed to determine the cutoff value. Additionally, there was no significant difference between LR and LI (aldosterone-corrected LR) in our study. Specifically, the LR values of cases 1, 2, 5, 9, and 10 were 1.18, 1.39, 1.03, 1.23 and 1.05, respectively, and the LI values were 1.04, 1.90, 1.10, 1.13, and 1.00, respectively. We did find changes in case 2 (from 1.39 to 1.90), which was closer to the reported critical value (2.0), but more cases are needed for the comparison between the two algorithms.

Bilateral adrenal adenomas are homogeneous or slightly heterogeneous on CT images¹⁴. PBMAH usually presents as typical diffuse or massively enlarged adrenal glands bilaterally with numerous nodules measuring up to 5 cm in diameter on CT scans. Sometimes it is difficult to distinguish BAA from PBMAH via CT. In our study, case 7 presented as bilateral solitary nodules surrounded by atrophic adrenal tissue and was supposed to be BAA. However, the AVS results showed that the left AV to IVC cortisol gradient was less than 6.5, indicating adrenal hyperplasia, which was consistent with the postoperative diagnosis of PBMAH.

AVS is minimally invasive and safe and has a high success rate. However, the success rates range widely across different institutions, from 42–96%, and are dependent on the experience and expertise of radiologists and the use of a center-specific protocol¹⁵. Another disadvantage of AVS is its high price, but in consideration of the complications and hospitalization costs associated with hypercortisolism and adrenal crisis due to unnecessary bilateral resection, the cost-effectiveness of AVS is worthy of recognition.

Cosyntropin stimulation during AVS, considered the better choice for primary hyperaldosteronism in some studies^{16, 17}, was not performed in our patients. Further studies are needed to determine whether AVS with cosyntropin stimulation is more accurate in judging the dominant secretory side in AICS.

Other methods, such as ¹³¹I-NP-59 scintigraphy, were reported to be useful in etiological diagnosis. ¹³¹I-NP-59 scintigraphic imaging of the activity of tumors originating from the adrenal cortex reflects the localization of functional adrenal masses with a sensitivity of 50.0% and specificity of 81.8%¹⁸. Due to its advantage of being noninvasive, it was even thought that ¹³¹I-NP-59 scintigraphy could replace catheterization of the adrenal veins. Several studies found that successfully performed scintigraphy imaging was consistent with AVS in cases of AICS with bilateral adrenal masses¹⁹. However, scintigraphy imaging is not widely used because it is unavailable in most hospitals in China and many other countries.

Our study is limited by a small sample size; consequently, we were unable to verify the cutoff value provided by a previous study to find an appropriate value that can be generalized.

Our study demonstrated that AVS was useful for identifying the dominant source of cortisol hypersecretion, accordingly solving the problem of adrenal resection decisions in patients with AICS and bilateral adrenal mass. In patients with failed AVS, the AV to IVC cortisol ratio and the presence of an adrenal mass could guide proper management. Long-term follow-up is indispensable to monitoring for possible repeat surgery, ensuring adequate hormonal replacement, and treating the psychological and multiorgan consequences of hypercortisolism.

Funding

This work was supported by the 1·3·5 project for disciplines of excellence–Clinical Research Incubation Project, West China Hospital, Sichuan University. NO. 2021HXFH008.

Competing Interests

No conflicts of interest, financial or otherwise, are declared by the author(s).

Author contributions

Yan Ren and Tao Chen conceived and designed research; Xingxing An, Dan Mo performed experiments; Xingxing An, Nianwei Wu, Sikui Shen, Dan Zhang, Tingting Zhang and Yuanmei Li analyzed data; Xingxing An, Tao Chen, Jianwei Li, Yuchun Zhu and Yan Ren interpreted results of experiments; Xingxing An and Dan Mo prepared figures; Xingxing An drafted manuscript; Haoming Tian, Tao Chen and Yan Ren edited and revised manuscript; Yuchun Zhu and Yan Ren approved final version of manuscript.

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of West China Hospital.

Consent to participate

Informed consent was obtained from all individual participants included in the study.

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Role of adrenal venous sampling in the differential diagnosis of ACTH-independent Cushing’s syndrome with bilateral adrenal mass

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Abstract

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Introduction

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Discussion

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References

Supplementary Files

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