# Desmopressin is a safe and effective secretagogue to replace corticotropin-releasing hormone in petrosal sinus sampling

Cecilia Piazzola, Thomas Graillon, Nadine Girard, Henry Dufour, Thierry Brue, Frederic Castinetti

► To cite this version:

Cecilia Piazzola, Thomas Graillon, Nadine Girard, Henry Dufour, Thierry Brue, et al. Desmopressin is a safe and effective secretagogue to replace corticotropin-releasing hormone in petrosal sinus sampling. Annales d'Endocrinologie = Annals of Endocrinology, 2025, 86 (2), pp.101678. 10.1016/j.ando.2024.101678. hal-05000004

HAL Id: hal-05000004

https://amu.hal.science/hal-05000004v1

Submitted on 21 Mar 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

Original article

# Desmopressin is a safe and effective secretagogue to replace corticotropin-releasing hormone in petrosal sinus sampling

Cecilia Piazzola<sup>a,b</sup>, Thomas Graillon<sup>a,c</sup>, Nadine Girard<sup>d</sup>, Henry Dufour<sup>a,c</sup>, Thierry Brue<sup>a,b</sup>, Frederic Castinetti<sup>a,b,*</sup>

## INFO ARTICLE

Keywords :

Pituitary

Cushing disease

Ectopic ACTH secretion

Bilateral inferior petrosal sinus sampling

Desmopressin

## ABSTRACT

**Purpose.** – Bilateral inferior petrosal sinus sampling (BIPSS) with corticotropin-releasing hormone (CRH) was the gold standard for distinguishing Cushing disease (CD) from ectopic ACTH secretion (EAS). CRH, however, is no longer available.

**Objective.** – To assess the reliability of BIPSS with desmopressin to differentiate CD from EAS.

**Methods.** – A retrospective study included patients who underwent BIPSS with desmopressin for ACTH-dependent hypercortisolism, with the whole diagnostic procedure in a single center.

**Results.** – Fifty-eight patients with confirmed etiological diagnosis were included: 51 CD, 7 EAS. Forty-three CD patients (84.3%) had post-stimulation ratio ≥ 2 before stimulation and 6 of the other 8 (75%) had a ratio ≥ 3. All EAS patients were correctly diagnosed before and after stimulation. Sensitivity was 84.3% before stimulation and 92.2% combining pre- and post-stimulation results; specificity reached 100%. A ROC curve established optimal thresholds at 1.4 before stimulation and 1.7 after.

**Conclusion.** – Desmopressin is a good substitute for CRH, correcting diagnosis compared to baseline BIPSS in 12% of cases.

© 2024 Les Auteurs. Published par Elsevier Masson SAS. Cet article est publié en Open Access sous licence

CC BY (http://creativecommons.org/licenses/by/4.0/).

## 1. Introduction

Differential diagnosis between Cushing's disease (CD) and ectopic ACTH secretion (EAS) can be challenging. While the need for bilateral inferior petrosal sinus sampling (BIPSS) has recently been questioned [1-3], recent guidelines advocate it, especially in patients with moderate hypercortisolism and/or equivocal imaging [4,5]. BIPSS involves baseline peripheral (P) and bilateral inferior petrosal sinus (IPS) measurements of ACTH, followed by the same measurements after injection of a secretagogue. Due to the recent worldwide shortage of corticotropin-releasing hormone (CRH), questions have been raised about the need for stimulation and the potential role of desmopressin [6,7]. Desmopressin is a selective V2 receptor agonist present in 90% of corticotrope pituitary adenomas [8], but may also be expressed by some ectopic tumors, leading to a false-positive response in about 20% of cases

[1]. In our center, desmopressin has been used as a secretagogue in most BIPSS since 1995. Our aim here was to report the results of desmopressin-stimulated BIPSS to differentiate CD from EAS.

## 2. Patients and methods

Consecutive patients with ACTH-dependent hypercortisolism were retrospectively included if they underwent BIPSS with 10 µg desmopressin stimulation for ACTH-dependent hypercortisolism between 1995 and 2023. Twenty-three patients with a specific diagnosis were already described in our first cohort study in 2007 [9] and were included in the current study because they had a complete diagnostic procedure and follow-up exclusively in our center.

BIPSS was performed by the same 3 radiologists over all the 30 years; only the X-ray equipment was updated in 2012. During BIPSS, the neuroradiologist performed bilateral femoral percutaneous venipuncture. On one side, venous catheterization was performed via the petrosal sinus. Blood samples were taken from both petrosal catheters and peripheral veins at baseline and then 5 and 15 minutes after administration of 10 µg desmopressin. No

<footnote><sup>a</sup> Aix Marseille Univ, INSERM, UMR1251, Marseille Medical Genetics, Institut MarMaRa, Marseille, France</footnote>

<footnote><sup>b</sup> AP-HM, Aix Marseille Univ, Department of Endocrinology, Hôpital La Conception, Institut MarMaRa, Marseille, France</footnote>

<footnote><sup>c</sup> AP-HM, Aix Marseille Univ, Department of Neurosurgery, Hôpital La Timone, Marseille, France</footnote>

<footnote><sup>d</sup> AP-HM, Aix Marseille Univ, Department of Neuroradiology, Hôpital La Timone, CNRS, CRMBM, UMR 7339, Marseille, France</footnote>

<footnote>* Corresponding author. Department of endocrinology, La Conception Hospital, 147, boulevard Baille, 13005 Marseille, France.
Adresse e-mail : frederic.castinetti@ap-hm.fr (F. Castinetti).</footnote>
<table><caption>**Table 1**

Patient characteristics and bilateral inferior petrosal sinus sampling results (median and interquartile range or number and percentage).</caption><thead><tr><th></th><th>CD (n=51)</th><th>EAS (n=7)</th><th>p-value</th></tr></thead><tbody><tr><td>Female, male, % female</td><td>37, 14, 72.5</td><td>4, 3, 57.1</td><td>0.4</td></tr><tr><td>Age</td><td>45 (31–53)</td><td>56 (36–58)</td><td>0.133</td></tr><tr><td>MRI</td><td></td><td></td><td></td></tr><tr><td>Visible adenoma, median size (mm)</td><td>24, 5 (2–9)</td><td>0</td><td>0.03</td></tr><tr><td>Doubtful</td><td>20</td><td>3</td><td></td></tr><tr><td>No image</td><td>7</td><td>3</td><td></td></tr><tr><td>CT image</td><td></td><td></td><td></td></tr><tr><td>Yes/no, % yes</td><td>3/20, 13</td><td>5/2, 71.4</td><td>0.007</td></tr><tr><td>ACTH (pg/mL)</td><td>49 (36–71)</td><td>138 (99–211)</td><td>0.006</td></tr><tr><td>Cortisol (nmol/L)</td><td>520 (420.8–621.5)</td><td>946 (519–1485)</td><td>0.019</td></tr><tr><td>UFC (nmol/24 h)</td><td>472 (273.8–1216)</td><td>5695 (1704–6864)</td><td>0.0001</td></tr><tr><td>Basal peripheral ACTH</td><td>39.3 (23–60)</td><td>120 (80–212)</td><td>0.0002</td></tr><tr><td>Maximum basal ACTH IPS</td><td>366 (109–785)</td><td>132 (71–271)</td><td>0.15</td></tr><tr><td>Maximum post-stimulation peripheral ACTH</td><td>99.2 (78–179)</td><td>175 (143–235)</td><td>0.024</td></tr><tr><td>Maximum post-stimulation ACTH IPS</td><td>1966 (569–2000)</td><td>202.5 (140–232.8)</td><td>0.0006</td></tr><tr><td>Higher basal IPS: P ratio</td><td>8.6 (4.8–15.2)</td><td>1.17 (1.05–1.28)</td><td>&lt;0.0001</td></tr><tr><td>Maximum post-stimulation IPS: P ratio</td><td>15.5 (8.9–27.8)</td><td>1.23 (1.16–1.42)</td><td>&lt;0.0001</td></tr></tbody></table>

Results were significant for *P* < 0.05. CD: Cushing disease; EAS: ectopic ACTH secretion; MRI: pituitary MRI; CT: computed tomography; UFC: urinary free cortisol; IPS:P: ratio of ACTH between inferior petrosal sinus and peripheral blood.

anticoagulation was used during this procedure. In our center, all cases of ACTH-dependent hypercortisolism are discussed in multidisciplinary board meetings: a joint decision for BIPSS can be taken when there is no formal 1.5 or 3 Tesla MRI image read by an expert neuroradiologist and/or when discordant results are observed on dynamic tests. In our center, patients who had BIPSS supporting pituitary secretion without a clear MRI image were not necessarily operated on, but might be treated with steroidogenesis inhibitors with regular MRI monitoring, as previously described. We thus only included patients for whom the final etiologic diagnosis was certain: positive pathology, biochemical remission after surgery or in whom an obvious pituitary adenoma became visible during follow-up [1]. In all other cases, patients were excluded from further analyses. Patients with cyclic Cushing disease were not included.

We first used standard cut-offs (IPS/P ACTH ≥ 2 before and ≥ 3 after stimulation) to determine the accuracy of desmopressin-stimulated BIPSS [10]. We then used a receiver operating characteristic (ROC) curve to determine our optimal cut-off to differentiate CD from EAS. All plasma ACTH measurements were performed in our lab, with an Elecsys Cobas (Roche Diagnostics) assay from 2009 and, before that date, by radio-immunoanalysis.

Statistical analysis used the non-parametric Mann-Whitney U test for continuous variables. Contingency tables were used with Fisher exact tests for variables with 2 options and Chi² for variables with more than 2 options.

According to our institutional policy, this retrospective study did not require specific signed informed consent from patients as the data collected were anonymized. It was approved by the Ethics Committee of Assistance Publique-Hôpitaux de Marseille (RGPD PADS reference SKJ9Y9-113_dgr).

# 3. Results

## 3.1. Clinical data

Seventy-two patients underwent BIPSS with desmopressin stimulation between 1995 and 2023. No complications were reported during the procedure, with no symptomatic hyponatremia after desmopressin injection. No specific fluid restriction was used in the 12 hours before the desmopressin injection. Fourteen patients were not included in the following analyses because of uncertain etiological diagnosis.

Fifty-eight patients had definite diagnosis: 51 with CD (87.9%) and 7 with EAS (12.1%). Patients with CD had visible adenoma in

47.1% of cases (24 patients; median size, 5 mm, range, 2–9 mm). MRI was equivocal in 39.2% of cases (20 patients), and negative in 13.7% (7 patients). In patients with EAS, MRI was equivocal (3 cases), negative (3 cases) or not available (1 case). Hormone levels were significantly lower in CD than EAS (Table 1). Only 22 patients had a desmopressin test prior to BIPPS; 20 of these, showed > 50% increase in ACTH and cortisol (19 CD and 1 EAS), 1 a 35% increase (CD), and 1 was non-responsive (CD). Only 16 patients underwent high-dose dexamethasone suppression testing; 10 showed > 69% reduction in cortisol (11): 9 CD and 1 EAS. Four the 6 patients who did not respond had CD and 2 had EAS: i.e., 69.2% sensitivity and 66.7% specificity.

## 3.2. BIPSS results

The median basal ratio (ratio of ACTH between maximum IPS and peripheral blood) was 8.57 for CD (range, 0.97–197.2) and 1.17 for EAS (range, 0.89–1.31) while the median maximum post-stimulation ratio was 15.5 for CD (range, 1.24–181.6) and 1.23 for EAS (range, 1.13–1.62). In the 22 patients with pre-BIPSS desmopressin test, the 2 patients with no or partial response (both CD) had a basal IPS:P gradient favoring CD, with respectively basal IPS:P ratio 14.2 and 7 and post-stimulation ratio 10.7 and 7.7. In patients with uncertain diagnosis, median basal ratio was 5.94 ± 6.92 and median post-stimulation ratio was 8.15 ± 11.06. With standard cut-offs, no EAS cases had basal IPS: *P* ≥ 2, or ≥ 3 after desmopressin stimulation. Forty-three of the 51 patients with CD (84.3%) had pre-stimulation basal IPS: *P* ≥ 2, and 8 (15.6%) < 2. Six of the 8 (75%) had a post-stimulation ratio > 3, in favor of CD (Fig. 1). Sensitivity and specificity were 84.3% and 100%, respectively, before stimulation, and 92.2% and 100% when pre- and post-stimulation results were combined. One of the 2 misdiagnosed patients had no previous desmopressin test and the other had a positive desmopressin test (350% increase in ACTH) and also responded during BIPSS with increased ACTH both peripherally and in the petrosal sinus, leading to a false negative ratio; however, this increase was more pronounced in the petrosal sinus (240% vs. 150%).

In our cohort, 19 patients with CD had urinary free cortisol (UFC) > 3 N; 26 had UFC < 3 N and 6 did not have this test. Thus, 42.2% of these 45 patients had UFC > 3 N, versus 100% of EAS patients. Fifteen of the 19 patients with CD with UFC > 3 N had a basal ratio > 2 and 3 of the other 4 patients had a post-stimulation ratio > 3. This leads to sensitivity of 94.7% and specificity of 100%, with desmopressin stimulation necessary in 15.8% of patients with CD.
<table><caption>**Table 2**
Performance of BIPSS with desmopressin to differentiate Cushing disease (CD) and ectopic ACTH secretion (EAS).</caption><thead><tr><th>Authors, date</th><th>Patients</th><th>Optimal basal ratio</th><th>Optimal post-desmopressin ratio</th><th>Sensitivity (%)</th><th>Specificity (%)</th></tr></thead><tbody><tr><td>Machado et al., 2006</td><td>47 CD, 9 EAS</td><td>&gt; 2</td><td>&gt; 3</td><td>92.1</td><td>100</td></tr><tr><td>Castinetti et al., 2007</td><td>33 CD, 7 EAS</td><td>&gt; 2</td><td>&gt; 2</td><td>97</td><td>100</td></tr><tr><td>Chen et al., 2019</td><td>226 CD, 24 EAS</td><td>&gt; 1.4</td><td>&gt; 2.8</td><td>97.8</td><td>100</td></tr><tr><td>De Almedia et al., 2023</td><td>48 CD, 2 EAS</td><td>&gt; 1.2</td><td>&gt; 1.57</td><td>97.9</td><td>100</td></tr><tr><td>Our study</td><td>51 CD, 7 EAS<sup>a</sup></td><td>&gt; 1.4</td><td>&gt; 1.7</td><td>96.1</td><td>100</td></tr></tbody></table>

CD: Cushing disease, EAS: ectopic ACTH secretion.

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Maximum inferior petrosal sinus to peripheral (IPS: *P*) ACTH ratio before (A) and after (B) desmopressin stimulation.</figcaption></figure>

### 3.3. Optimal ratio to differentiate CD and EAS

We then used a ROC curve to determine the optimal cut-off to differentiate CD from EAS. The optimal basal ratio was 1.4, with 88.2% sensitivity and 100% specificity (*P* = 0.0002; AUC = 0.94; CI: [0.88–1]) and 1.7 after stimulation with 96.1% sensitivity and 100% specificity (*P* = 0.0001; AUC = 0.9869; CI: [0.962–1]). The maximum ratio was obtained 5 minutes after stimulation in 88% of patients (*n* = 51).

Table 2 shows the performance of BIPSS with desmopressin in the literature for differentiating CD and EAS.

### 3.4. Analysis of lateralization data

Data on the side of the adenoma were available for 37 patients with CD. Twenty-five had a lateralization ratio >1.4 between the two sides: 13 on the right and 12 on the left, with significant correlation (*P* = 0.03) observed between lateralization ratio and the side of the adenoma, enabling correct diagnosis in 17 patients (68%). Interestingly, 6 of the 12 patients with CD without >1.4 lateraliza-

tion ratio (50%) had a basal IPS:P ratio <2. In the 38 patients with lateralization ratio >1.4, only 2 (5.3%) had a basal IPS:P ratio <2 (*P* = 0.0004).

## 4. Discussion

The etiological steps of the diagnosis of ACTH dependent Cushing's syndrome can be challenging and might include CRH testing, high dose dexamethasone suppression tests and/or desmopressin test. Apart from CRH, now lacking, the results of the 2 other tests are controversial [11]. BIPSS is still considered the gold standard in this approach. Baseline BIPPS results provided correct diagnosis in 86.2% of cases. Desmopressin stimulation correctly identified 75% of the cases misdiagnosed at baseline: i.e., 11.8% of cases were correctly diagnosed only after desmopressin stimulation. Although our cohort was smaller than that of Detomas et al. [12], our results seem to be at least comparable to those they reported with CRH stimulation, with 81.1% basal and 87.7% post-stimulation sensitivity, and 85.7% specificity, unchanged after stimulation. In our cohort, specificity reached 100% with all EAS cases correctly diagnosed on BIPSS.

To distinguish CD from EAS, we identified a baseline cut-off of 1.4, which was the same as found by Chen et al. [13] in their large cohort of desmopressin-stimulated BIPSS. These authors questioned the need for stimulation, because only 3.1% of the patients had misdiagnosis corrected with desmopressin: i.e., a modest 3% gain in sensitivity and unchanged specificity after stimulation. Their optimal post-stimulation threshold was 2.8. In our cohort, we, surprisingly, found a new post-stimulation threshold of 1.7. This new ratio gave a sensitivity gain of 4% but failed to identify the 2 patients with CD previously misdiagnosed with the standard ratios. For CRH, Detomas et al. [12] reported a cut-off of 1.9 at baseline and 2.1 after stimulation, with a sensitivity gain of 2% sensitivity and correction of diagnosis in 2 patients (1.7% of patients) compared to standard ratios. The optimal cut-off to differentiate CD from EAS remains controversial, and would require large collaborative studies, also considering the immunoassays used to define a universal threshold. In our cohort, the maximum ratio for patients with EAS was 1.31, in agreement with other studies [14–16]. Interestingly, focusing on patients with negative or doubtful MRI, the sensitivity and specificity of the BIPSS were both 100%.

Thus, all studies of BIPSS with desmopressin reported higher specificity than with CRH. It is possible that injection close to the pituitary gland results in peripheral dilution and hence low secretion from the ectopic tumor. Another explanation could be that some ectopic tumors secrete both CRH and ACTH [17,18], even if CRH is not systematically measured, which could result in permanent stimulation of the pituitary gland by CRH, reducing specificity.

While centers with high levels of expertise in pituitary MRI reported 20–30% negative or equivocal MRI scans, the present results showed that BIPSS can be considered as the gold standard in equivocal cases. Furthermore, the lateralization ratio achieved accuracy in 68% of cases, which is similar to the 69% accuracy reported in the literature [19]. Additionally, our results are consistent

<footnote>a 23 patients from Castinetti, 2007 were included in this current study.</footnote>
with those of Chen et al. [20], who recently showed that lack of lateralization (i.e., ratio < 1.4) predicted reduced sensitivity for diagnosis of CD. This also demonstrates the representativeness of our cohort and the generalizability of our findings. However, it should be noted that the ACTH assay was changed in 2009. We therefore performed the analyses using the data from each assay and found the same optimal cut-off values. It should also be noted that, in our center, prolactin measurement is not used to confirm correct catheterization, as its contribution is controversial for BIPSS with desmopressin [21]. We thus focus only on our team of expert neuoradiologists, considering that the injection of the radiocontrast agent confirms that the guide has been correctly inserted.

Finally, the fact that BIPSS is an invasive procedure has led authors to propose alternatives, the majority of which, however, are hampered by the shortage of CRH. The high-dose dexamethasone suppression test was not systematically performed in our center because its efficacy was controversial, according to recent guidelines on diagnosis of Cushing's syndrome [3]. In the few patients in our cohort who underwent this test prior to BIPSS, diagnostic benefit was modest, with 5/16 patients misdiagnosed. Moreover, some studies showed that MRI is better than high-dose dexamethasone suppression test to differentiate CD from EAS [22]. Other imaging modalities appear insufficient to identify primary EAS lesions, as sensitivity is 60% in occult secretion, which is clearly inferior to BIPSS [23].

Recently, it was suggested that UFC may be the most effective test to differentiate CD from EAS [2], arguing that patients with UFC < 3-fold the upper limit of normal (ULN) always have CD. However, UFC needs to be repeated several times to be reliable, with measurement variability up to 50%, especially in moderate hypersecretion [24]. In our cohort, patients with EAS all had UFC > 3 × ULN, and the 27/58 patients with UFC < 3 × ULN all had CD. As some previous studies, including multicenter studies, reported that up to 20% of cases of indolent EAS could present UFC below 3 × ULN [25,26], we still believe that UFC should be included in a global probabilistic approach that also takes into account epidemiological parameters, severity and timing of onset of comorbidities [27], hormone levels and imaging results, as well as, if necessary, desmopressin-stimulated BIPSS. In addition, non-invasive tests are currently under investigation, such as dynamic salivary cortisol tests [28].

## 5. Conclusion

In conclusion, in a cohort of patients requiring BIPSS according to current recommendations, desmopressin stimulation proved to be a reliable substitute for CRH to differentiate CD from EAS. Our results also confirmed that stimulation is ultimately required in only a small subset of patients (here, 12%) to correct the initial diagnosis [29].

## Funding information

No funding.

## Disclosure of interest

The authors declare that they have no competing interest.

## Acknowledgments

The authors would like to thank Pr. Andre Lacroix, Dr. Nicolas Sahakian, Dr. Isabelle Morange, Dr. Frederique Albarel, Dr. Benoit Testud and Pr. Jean Regis for fruitful discussions.

## Références

[1] Frete C, Corcuff JB, Kuhn E, Salenave S, Gaye D, Young J, et al. Non-invasive Diagnostic Strategy in ACTH-dependent Cushing's Syndrome. J Clin Endocrinol Metab 2020;105:3273-84, http://dx.doi.org/10.1210/clinin/dgaa409.

[2] Lavoillotte J, Mohammedi K, Salenave S, Furnica RM, Maiter D, Chanson P, et al. Personalized non-invasive diagnostic algorithms based on urinary free cortisol in ACTH-dependant Cushing's syndrome. J Clin Endocrinol Metab 2024;dgae258, http://dx.doi.org/10.1210/clinin/dgae258 [Online ahead of print].

[3] Martinerie L, Bouligand J, North MO, Bertherat J, Assié G, Espiard S. Consensus statement by the French Society of Endocrinology (SFE) and French Society of Pediatric Endocrinology & Diabetology (SFEDP) for the diagnosis of Cushing's syndrome: Genetics of Cushing's syndrome. Ann Endocrinol Metab 2024;85:284-93, http://dx.doi.org/10.1016/j.ando.2024.01.005.

[4] Tabarin A, Assié G, Barat P, Bonnet F, Bonneville JF, Borson-Chazot F, et al. Consensus statement by the French Society of Endocrinology (SFE) and French Society of Pediatric Endocrinology & Diabetology (SFEDP) on diagnosis of Cushing's syndrome. Ann Endocrinol Metab 2022;83:119-41, http://dx.doi.org/10.1016/j.ando.2022.02.001.

[5] Fleseriu M, Auchus R, Bancos I, Ben-Shlomo A, Bertherat J, Biermasz NR, et al. Consensus on diagnosis and management of Cushing's disease: a guideline update. Lancet Diab Endocrinol 2021;9:847-75, http://dx.doi.org/10.1016/S2213-8587(21)00235-7.

[6] Keyzer Y, de, Lenne F, Auzan C, Jégou S, René P, et al. The pituitary V3 vasopressin receptor and the corticotroph phenotype in ectopic ACTH syndrome. J Clin Investig 1996;97:1311-8, http://dx.doi.org/10.1172/JCI118547.

[7] Castinetti F, Lacroix A. Is desmopressin useful in the evaluation of Cushing Syndrome? J Clin Endocrinol Metab 2022;107:e4295-301, http://dx.doi.org/10.1210/clinin/dgac533.

[8] Wang F, Tang K, Yen Y, Ho DM, Yang A, Hwang C, et al. Plasma corticotrophin response to desmopressin in patients with Cushing's disease correlates with the expression of vasopressin receptor 2, but not with that of desmopressin receptor 1 or 3, in their pituitary tumours. Clin Endocrinol 2012;76:253-63, http://dx.doi.org/10.1111/j.1365-2265.2011.04179.x.

[9] Castinetti F, Morange I, Dufour H, Jaquet P, Conte-Devolx B, Girard N, et al. Desmopressin test during petrosal sinus sampling: a valuable tool to discriminate pituitary or ectopic ACTH-dependent Cushing's syndrome. Eur J Endocrinol 2007;157:271-7, http://dx.doi.org/10.1530/EJE-07-0215.

[10] Oldfield EH, Doppman JL, Nieman LK, Chrousos GP, Miller DL, Katz DA, et al. Petrosal Sinus Sampling with and without Corticotropin-Releasing Hormone for the Differential Diagnosis of Cushing's Syndrome. N Engl J Med 1991;325:897-905, http://dx.doi.org/10.1056/NEJM199109263251301.

[11] Elenius H, McGlotten R, Nieman LK. Ovine CRH Stimulation and 8 mg Dexamethasone Suppression Tests in 323 patients with ACTH-dependent Cushing's Syndrome. J Clin Endocrinol Metab 2023;109:e182-9, http://dx.doi.org/10.1210/clinin/dgad454.

[12] Detomas M, Ritzel K, Nasi-Kordhishti I, Scherntnaner-Reiter MH, Losa M, Tröger V, et al. Bilateral inferior petrosal sinus sampling with human CRH stimulation in ACTH-dependent Cushing's syndrome: results from a retrospective multicenter study. Eur J Endocrinol 2023;188:448-56, http://dx.doi.org/10.1093/ejendo/lvad050.

[13] Chen S, Chen K, Wang S, Zhu H, Lu L, Zhang X, et al. The optimal cut-off of BIPSS in Differential Diagnosis of ACTH-dependent Cushing's Syndrome: is stimulation necessary? J Clin Endocrinol Metab 2020;105:e1673-85, http://dx.doi.org/10.1210/clinin/dgz194.

[14] Ilias I, Chang R, Pacak K, Oldfield EH, Wesley R, Doppman J, et al. Jugular venous sampling: an alternative to petrosal sinus sampling for the diagnostic evaluation of adrenocorticotropic hormone-dependent Cushing's Syndrome. J Clin Endocrinol Metab 2004;89:3795-800, http://dx.doi.org/10.1210/jc.2003-03204.

[15] Machado MC, De Sa SV, Domenice S, Fragoso MCBV, Puglia P, Pereira MAA, et al. The role of desmopressin in bilateral and simultaneous inferior petrosal sinus sampling for differential diagnosis of ACTH-dependent Cushing's syndrome. Clin Endocrinol 2007;66:136-42, http://dx.doi.org/10.1111/j.1365-2265.2006.02700.x, 061120012318003-???

[16] Tsagarakis S, Vassiliadi D, Kaskarelis IS, Kominos J, Souvatzoglou E, Thalassinos N. The application of the combined corticotropin-releasing hormone plus desmopressin stimulation during petrosal sinus sampling is both sensitive and specific in differentiating patients with Cushing's disease from patients with the occult ectopic adrenocorticotropin syndrome. J Clin Endocrinol Metab 2007;92:2080-6, http://dx.doi.org/10.1210/jc.2006-2691.

[17] Elliott PF, Berhane T, Ragnarsson O, Falhammar H. Ectopic ACTH- and/or CRH-Producing Pheochromocytomas. J Clin Endocrinol Metab 2021;106:598-608, http://dx.doi.org/10.1210/clinin/dgaa488.

[18] Ragnarsson O, Juhlin CC, Torpy DJ, Falhammar H. A clinical perspective on ectopic Cushing's syndrome. Trends Endocrinol Metab 2024;35:347-60, http://dx.doi.org/10.1016/j.tem.2023.12.003.

[19] Wind JJ, Lonser RR, Nieman LK, DeVroom HL, Chang R, Oldfield EH. The lateralization accuracy of inferior petrosal sinus sampling in 501 patients with Cushing's disease. J Clin Endocrinol Metab 2013;98:2285-93, http://dx.doi.org/10.1210/jc.jc2012-3943.

[20] Chen S, Lyu X, Hong W, Zhang D, Zhang Y, Yang D, et al. Bilateral inferior petrosal sinus sampling without lateralization is less accurate for the diagnosis of Cushing Disease. J Endocr Soc 2024;8, http://dx.doi.org/10.1210/jendso/bvae056, bvae056.
[21] Akbari H, Ghorbani M, Kabootari M, Mehrjardi AZ, Mohajeri Tehrani MR, Malek M, et al. Usefulness of prolactin measurement in inferior petrosal sinus sampling with desmopressin for Cushing's syndrome. Br J Neurosurg 2020;34:253-7, http://dx.doi.org/10.1080/02688697.2020.1736263.

[22] Shi X, Du T, Zhu D, Ma D, Dong K, Peng X, et al. High-dose dexamethasone suppression test is inferior to pituitary dynamic enhanced MRI in the differential diagnosis of ACTH-dependent Cushing's syndrome. Endocrine 2022;75:516-24, http://dx.doi.org/10.1007/s12020-021-02891-y.

[23] Channaiah CY, Memon SS, Lila AR, Sarathi V, Karlekar M, Barnabas R, et al. Diagnostic performance of various imaging modalities in localizing ectopic ACTH syndrome: a systematic review. Ann Endocrinol 2024, http://dx.doi.org/10.1016/j.ando.2024.07.001. S0003426624001094 [Online ahead of print].

[24] Petersen S, Newell-Price J, Findling JW, Gu F, Maldonado M, Sen K, et al. High variability in baseline urinary free cortisol values in patients with Cushing's disease. Clin Endocrinol 2014;80:261-9, http://dx.doi.org/10.1111/cen.12259.

[25] Ilias I, Torpy DJ, Pacak K, Mullen N, Wesley RA, Nieman LK. Cushing's Syndrome due to ectopic corticotropin secretion: twenty years' experience at

the National Institutes of Health. J Clin Endocrinol Metab 2005;90:4955-62, http://dx.doi.org/10.1210/jc.2004-2527.

[26] Ejaz S, Vassilopoulou-Sellin R, Busaidy NL, Hu MI, Waguespack SG, Jimenez C, et al. Cushing's syndrome secondary to ectopic ACTH secretion: the University of Texas MD Anderson Cancer Center Experience. Cancer 2011;117:4381-9, http://dx.doi.org/10.1002/cncr.26029.

[27] Araujo-Castro M, Pascual-Corrales E, Lamas C. Possible, probable, and certain hypercortisolism: a continuum in the risk of comorbidity. Ann Endocrinol 2023;84:272-84, http://dx.doi.org/10.1016/j.ando.2023.01.005.

[28] Laguillier-Morizot C, Bonnet-Serrano F, Leguy MC, Simeonovic M, Sée C, Zientek C, et al. Diagnostic performance of an automated immunoassay for salivary cortisol. Ann Endocrinol 2024;85:20-6, http://dx.doi.org/10.1016/j.ando.2023.10.007.

[29] Almeida de TS, Rodrigues da CT, Costenaro F, Scaffaro LA, Farenzena M, Gastaldo F, et al. Enhancing Cushing's disease diagnosis: exploring the impact of desmopressin on ACTH gradient during BIPSS. Front Endocrinol 2023;14:1224001, http://dx.doi.org/10.3389/fendo.2023.1224001.