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Review
. 2025 Nov 18;110(12):3559-3568.
doi: 10.1210/clinem/dgaf396.

Approach to the Patient With Primary Aldosteronism: Role of Molecular Imaging

Ada E D Teo  1   2 , Hieu T N Tran  3   4   5 , Chin Meng Khoo  1   2 , Ismail Osman  3 , Aaron Kian-Ti Tong  6 , Roger S Y Foo  2   7 , Troy H Puar  3   4
Affiliations
Review

Approach to the Patient With Primary Aldosteronism: Role of Molecular Imaging

Ada E D Teo et al. J Clin Endocrinol Metab. .

Abstract

A common yet underdiagnosed cause of secondary hypertension, primary aldosteronism (PA) is characterized by excess aldosterone production, causing hypertension with increased risk of cardio-renal-metabolic complications. Accurate and timely localization of the source of aldosterone excess is crucial for management, in the form of curative adrenalectomy for unilateral aldosterone-producing adenoma or medical management for bilateral adrenal hyperplasia. The current diagnostic algorithm involves adrenal vein sampling (AVS) as the current "gold standard" in determining lateralization of aldosterone secretion, but its technical challenges present significant barriers to timely diagnosis and treatment. Recent technological advancements have contributed to the evolution of molecular imaging modalities such as 11C-metomidate positron emission tomography-computed tomography (11C-MTO PET-CT). Improved molecular imaging modalities hold significant potential to complement existing diagnostic pathways and refine treatment strategies for PA. This review evaluates different case scenarios comparing the utility of AVS with 11C-MTO PET-CT, suggesting a practical approach for its interpretation and highlighting the clinical decision-making process.

Keywords: functional/nuclear imaging; laparoscopic adrenalectomy; secondary hypertension; steroid hybrid hormones; subtyping.

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Figures

Figure 1.
Figure 1.
11C-MTO PET-CT for case 1—right adrenal nodule (white arrow) seen on CT imaging (A) with a high SUVmax over the right adenoma (32.7) compared to the left adrenal gland (18.7) on the fused PET-CT imaging (B) and PET imaging (C). The SUVmax ratio of right adrenal nodule-to-contralateral gland was 1.75 (greater than cutoff of 1.25 to define lateralization). Abbreviations: 11C-MTO PET-CT, 11C-metomidate positron emission tomography-computed tomography; SUVmax, maximum standardized uptake value.
Figure 2.
Figure 2.
11C-MTO PET-CT for case 2—bilateral adrenal nodules seen on CT imaging (A) with a high SUVmax over the left adenoma (64.4) (white arrow) compared to the right adrenal gland (51.1) (black arrow) on the fused PET-CT imaging (B) and PET imaging (C). The SUVmax ratio of left adrenal nodule-to-contralateral gland was 1.26 (greater than cutoff of 1.25 to define lateralization). Abbreviations: 11C-MTO PET-CT, 11C-metomidate positron emission tomography-computed tomography; SUVmax, maximum standardized uptake value.
Figure 3.
Figure 3.
11C-MTO PET-CT for case 3—right adrenal nodule seen on CT imaging (A) with low SUVmax over the right medial limb nodule (25.5) compared to the left adrenal gland (28.1) on the fused PET-CT imaging (B) and PET imaging (C). The SUVmax ratio of right adrenal nodule-to-contralateral gland was 0.91 (less than cutoff of 1.25 to define lateralization). Abbreviations: 11C-MTO PET-CT, 11C-metomidate positron emission tomography-computed tomography; SUVmax, maximum standardized uptake value.
Figure 4.
Figure 4.
11C-MTO PET-CT for case 4—no adrenal lesion seen on CT imaging (A). AVS showed clear left lateralization, but MTO detected a left adrenal nodule with only SUVmax 45.2, compared to SUVmax of 39.5 over the right adrenal body on the fused PET-CT imaging (B) and PET imaging (C). The SUVmax ratio of left adrenal nodule-to-contralateral gland was 1.14 (less than cutoff of 1.25 to define lateralization). Abbreviations: 11C-MTO PET-CT, 11C-metomidate positron emission tomography-computed tomography; AVS, adrenal vein sampling; SUVmax, maximum standardized uptake value.
Figure 5.
Figure 5.
11C-MTO PET-CT for case 5—3 small left adrenal nodules detected on CT imaging (A). MTO showed 2 nodules over left lateral limb with high uptake of SUVmax 54.7 (lateral most nodule 1.0 cm) and SUVmax 33.4 (medial most nodule 0.6 cm), compared to the right adrenal gland (34.4) on the fused PET-CT imaging (B) and PET imaging (C). The SUVmax ratio of left adrenal nodules to contralateral gland was 1.59 and 0.97, respectively (compared to cutoff of 1.25 to define lateralization). Abbreviations: 11C-MTO PET-CT, 11C-metomidate positron emission tomography-computed tomography; SUVmax, maximum standardized uptake value.
Figure 6.
Figure 6.
Main radiotracers developed over the past decade and their binding locations. Created with BioRender.com.
Figure 7.
Figure 7.
Proposed future algorithm for subtyping PA. Current data suggests that each subtype test is highly specific. Hence, this algorithm recommends that they can be used sequentially, moving from the least to the most invasive: hybrid hormone/steroid panel algorithm, molecular imaging, and adrenal vein sampling. *Clear lateralization for 11C-MTO PET-CT uses an SUVmax ratio of greater than 1.25; thresholds with other radiotracers would differ. Abbreviations: 11C-MTO PET-CT, 11C-metomidate positron emission tomography-computed tomography; AVS, adrenal vein sampling; NA, not available; PA, primary aldosteronism; SUVmax, maximum standardized uptake value.
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