Adrenal (131)I-6β-iodomethylnorcholesterol scintigraphy in choosing the side for adrenalectomy in bilateral adrenal tumors with subclinical hypercortisolemia

Development of Fluorinated NP-59: A Revival of Cholesterol Use Imaging with PET

Imaging of cholesterol use is possible with the ¹³¹I scintiscanning/SPECT agent NP-59. This agent provided a noninvasive measure of adrenal function and steroid synthesis. However, iodine isotopes resulted in poor resolution, manufacturing challenges, and high radiation dosimetry to patients that have limited their use and clinical impact. A ¹⁸F analog would address these shortcomings while retaining the ability to image cholesterol use. The goal of this study was to prepare and evaluate a ¹⁸F analog of NP-59 to serve as a PET imaging agent for functional imaging of the adrenal glands based on cholesterol use. Previous attempts to prepare such an analog of NP-59 have proven elusive. Preclinical and clinical evaluation could be performed once the new fluorine analog of NP-59 production was established. Methods: The recent development of a new reagent for fluorination along with an improved route to the NP-59 precursor allowed for the preparation of a fluorine analog of NP-59, FNP-59. The radiochemistry for the ¹⁸F-radiolabeled ¹⁸F-FNP-59 is described, and rodent radiation dosimetry studies and in vivo imaging in New Zealand rabbits was performed. After in vivo toxicity studies, an investigational new drug approval was obtained, and the first-in-humans images with dosimetry using the agent were acquired. Results: In vivo toxicity studies demonstrated that FNP-59 is safe for use at the intended dose. Biodistribution studies with ¹⁸F-FNP-59 demonstrated a pharmacokinetic profile similar to that of NP-59 but with decreased radiation exposure. In vivo animal images demonstrated expected uptake in tissues that use cholesterol: gallbladder, liver, and adrenal glands. In this first-in-humans study, subjects had no adverse events and images demonstrated accumulation in target tissues (liver and adrenal glands). Manipulation of uptake was also demonstrated with patients who received cosyntropin, resulting in improved uptake. Conclusion: ¹⁸F-FNP-59 provided higher resolution images, with lower radiation dose to the subjects. It has the potential to provide a noninvasive test for patients with adrenocortical diseases.

The role of adrenal venous sampling (AVS) in primary bilateral macronodular adrenocortical hyperplasia (PBMAH): a study of 16 patients

OBJECTIVE

Primary bilateral macronodular adrenocortical hyperplasia (PBMAH) is a rare cause of ACTH-independent Cushing's syndrome. Current guidelines recommend bilateral adrenalectomy for PBMAH, but several studies showed clinical effectiveness of unilateral adrenalectomy despite bilateral disease in selected patients. Our aim was to evaluate the gain of information which can be obtained through adrenal venous sampling (AVS) based cortisol lateralization ratios for guidance of unilateral adrenalectomy.

DESIGN

We performed a retrospective analysis of 16 patients with PBMAH and clinical overt cortisol secretion in three centers METHODS: Selectivity of adrenal vein sampling during AVS was defined as a gradient of cortisol or a reference adrenal hormone ≥2.0 between adrenal and peripheral vein. Lateralization was assumed if the dominant to non-dominant ratio of cortisol to reference hormone was ≥4.0.

RESULTS

AVS was technically successful in all patients based on absolute cortisol levels and in 13 of 16 patients (81%) based on reference hormone levels. Lateralization was documented in 8 of 16 patients. In patients with lateralization, in 5 of 8 cases this occurred toward morphologically larger adrenals, while in 3 patients lateralization was present in bilaterally identical adrenals. The combined volume of adrenals correlated positively with urinary free cortisol, suggesting that adrenal size is the dominant determinant of cortisol secretion.

CONCLUSIONS

In this study the gain of information through AVS for unilateral adrenalectomy was limited in patients with PBMAH and marked adrenal asymmetry.

Consensus statement by the French Society of Endocrinology (SFE) and French Society of Pediatric Endocrinology & Diabetology (SFEDP) on diagnosis of Cushing's syndrome

Cushing's syndrome is defined by prolonged exposure to glucocorticoids, leading to excess morbidity and mortality. Diagnosis of this rare pathology is difficult due to the low specificity of the clinical signs, the variable severity of the clinical presentation, and the difficulties of interpretation associated with the diagnostic methods. The present consensus paper by 38 experts of the French Society of Endocrinology and the French Society of Pediatric Endocrinology and Diabetology aimed firstly to detail the circumstances suggesting diagnosis and the biologic diagnosis tools and their interpretation for positive diagnosis and for etiologic diagnosis according to ACTH-independent and -dependent mechanisms. Secondly, situations making diagnosis complex (pregnancy, intense hypercortisolism, fluctuating Cushing's syndrome, pediatric forms and genetically determined forms) were detailed. Lastly, methods of surveillance and diagnosis of recurrence were dealt with in the final section.

Adrenal Vein Cortisol to Metanephrine Ratio for Localizing ACTH-Independent Cortisol-Producing Adenoma: A Case Report

Context

Finding the source of adrenocorticotropic hormone (ACTH)-independent cortisol-producing adenoma in the patients with subclinical Cushing syndrome (SCS) and bilateral adrenal nodules is sometimes challenging. Computed tomography (CT) and positron emission tomography are helpful, but adrenal venous sampling (AVS) is the gold standard approach. However, interpretation of AVS is important to improve the accuracy of decision-making for surgery. We report a case and review of the literature to assess the benefit of using adrenal vein cortisol to metanephrine ratio to determine the source of cortisol production in SCS and bilateral nodules.

Evidence Acquisition

Three authors searched PubMed for data on patients with SCS who had AVS procedure and measurements of cortisol and catecholamines.

Case Description

A 51-year-old woman with SCS and hypertension crisis presented to our clinic. Paraclinical investigations revealed that she had an ACTH-independent cortisol-producing adenoma and her CT scan showed bilateral adrenal nodules. After AVS, cortisol (high to low) lateralization ratio could not determine the source of cortisol production but the cortisol to metanephrine ratio localized the source to the left side, which included the larger nodule according to CT measurements. Left adrenalectomy led to clinical and paraclinical improvement.

Conclusion

There is a possibility of co-secretion of other steroids accompanied with cortisol in the setting of ACTH-independent SCS. Moreover, cortisol measurement alone and interpretation of AVS results based on cortisol values may not help lateralizing the source of cortisol production with bilateral adrenal nodules. Therefore, we suggest applying cortisol to metanephrine ratio with the same gradient (gradient > 2.3, highest to lowest concentration) when the source of cortisol production cannot be determined by cortisol lateralization ratio.

Adrenal Imaging in Patients with Endocrine Hypertension

Hypertension is one of the commonest chronic diseases contributing to cardiovascular disease. Idiopathic (primary) hypertension accounts for approximately 85% of the diagnosed cases, and 15% of hypertensive patients have other contributing conditions leading to elevated blood pressure (secondary hypertension). Endocrine hypertension is a common secondary cause of hypertension. The most common causes of endocrine hypertension are excess production of mineralocorticoids (ie, primary hyperaldosteronism), glucocorticoids (Cushing syndrome), and catecholamines (pheochromocytoma). After biochemical confirmation of hormonal excess, appropriate use of imaging modalities, both functional and anatomic, should occur for the diagnostic workup of these patients and for location of the source of hormonal excess.

Adrenal Venous Sampling for Assessment of Autonomous Cortisol Secretion

CONTEXT

Autonomous cortisol secretion (ACS) can be unilateral or bilateral irrespective of the presence of an adrenal tumor. A reliable method to distinguish between unilateral and bilateral ACS is lacking.

OBJECTIVE

Evaluate the use of adrenal venous sampling (AVS) to distinguish between unilateral and bilateral ACS.

DESIGN AND METHODS

This was a prospective study of AVS in patients with adrenal tumors who received a diagnosis of ACS or adrenal Cushing syndrome (CS). Unilateral secretion was defined as >2.3-fold difference in cortisol levels between the two adrenal veins. Metanephrine levels were used to ascertain correct catheter position. Results were correlated with findings on CT and iodine-131-cholesterol scintigraphy.

RESULTS

Thirty-nine patients underwent AVS; there were no complications. The procedure was inconclusive in six patients and repeated with success in one, giving a success rate of 85%, and leaving 34 procedures for evaluation (adrenal CS, n = 2; ACS, n = 32). Of 14 patients with bilateral tumors, 10 had bilateral and 4 had unilateral overproduction. Of 20 patients with unilateral tumors, 11 had lateralization to the side of the tumor and the remaining had bilateral secretion. Cholesterol scintigraphy findings were concordant with those of AVS in 13 of 18 cases (72%) and discordant in 5 (28%).

CONCLUSION

Laterality of ACS does not always correspond to findings on CT images. AVS is a safe and valuable tool for differentiation between unilateral and bilateral cortisol secretion and should be considered when operative treatment of ACS is a possibility.

Recent Advances on Subclinical Hypercortisolism

During the last 20 years, a significant body of literature has accumulated regarding subclinical hypercortisolism in patients with adrenal incidentalomas. Retrospective studies have indicated these patients have an increase in cardiovascular events and mortality. Current recommendations for patients with adrenal incidentalomas include an overnight low-dose dexamethasone suppression test and a thorough evaluation of cardiovascular and metabolic risk factors. Further hormonal testing and close monitoring are necessary in patients with incomplete suppression. Unilateral adrenalectomy may be beneficial in cases with abnormal suppression and comorbidities related to hypercortisolemia. Prospective studies are need for a better risk stratification and tailored therapy.