Evaluation of the sensitivity and specificity of (11)C-metomidate positron emission tomography (PET)-CT for lateralizing aldosterone secretion by Conn's adenomas

J Clin Endocrinol Metab. 2012 Jan;97(1):100-9. doi: 10.1210/jc.2011-1537. Epub 2011 Nov 23.


Context: Identification of unilateral aldosterone-producing (Conn's) adenomas has traditionally required lateralization by the invasive and technically difficult procedure of adrenal vein sampling (AVS). (11)C-metomidate, a potent inhibitor of adrenal steroidogenic enzymes, is a positron emission tomography (PET) radiotracer that is selectively accumulated by Conn's adenomas.

Objective: The objective of the study was to compare the sensitivity and specificity of (11)C-metomidate PET-computed tomography (CT) against the current gold standard of AVS.

Design: The design of the study was within-patient comparison of diagnostic techniques.

Setting: The study was conducted at a single center-university teaching hospital.

Patients: Thirty-nine patients with primary hyperaldosteronism (PHA) and five with nonfunctioning adenomas (incidentalomas) participated in the study.

Intervention(s): The first six PHA patients were studied on three occasions to determine whether steroid pretreatment reduced (11)C-metomidate uptake by normal adrenal. Subsequent patients received dexamethasone for 3 d prior to injection of (11)C-metomidate 150-500 MBq.

Main outcome measure(s): Maximum standardized uptake values (SUV(max)) over regions of interest determined from 35-45 min after injection were measured.

Results: Dexamethasone increased tumor to normal adrenal SUV(max) ratio by 25.6 ± 5.0% (P < 0.01). PET-CT visualized subcentimeter adenomas and distinguished hot from cold adenomas within a gland. In 25 patients with PHA and AVS lateralization to the side of an adenoma, SUV(max) over tumor (mean ± sem) of 21.7 ± 1.6 was greater than over normal adrenal, 13.8 ± 0.6 (P = 0.00003); this difference was absent in 10 patients without lateralization on AVS (P = 0.28) and in four of five incidentalomas. On receiver-operator characteristics analysis, an SUV(max) ratio of 1.25:1 provided a specificity of 87% [95% confidence interval (69, 104)] and sensitivity of 76% (59, 93); in tumors with SUV(max) greater than 17, the specificity rose to 100%.

Conclusions: (11)C-metomidate PET-CT is a sensitive and specific noninvasive alternative to AVS in the management of PHA.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Cortex Neoplasms / diagnostic imaging*
  • Adrenal Cortex Neoplasms / metabolism
  • Adrenocortical Adenoma / diagnostic imaging*
  • Adrenocortical Adenoma / metabolism
  • Adult
  • Aldosterone / metabolism*
  • Carbon Radioisotopes
  • Etomidate / analogs & derivatives*
  • Humans
  • Incidental Findings
  • Middle Aged
  • Multimodal Imaging / methods*
  • Positron-Emission Tomography*
  • ROC Curve
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed*


  • Carbon Radioisotopes
  • Aldosterone
  • metomidate
  • Etomidate