title: 131I-6 beta-iodomethylnorcholesterol scintigraphy: an assessment of its role in the investigation of adrenocortical incidentalomas.
abstract: OBJECTIVE
  Most incidentally discovered adrenal tumours ('incidentaloma') are benign adrenocortical adenomas. It has been suggested that 131I-6 beta-iodomethylnorcholesterol (IMC) scan could specify the degree of functional autonomy of such adenomas depending on whether they prevent contralateral adrenal tracer uptake. Our purpose was to examine this hypothesis in a correlated scintigraphic and endocrine study.
  
  
  METHODS
  Prospective study evaluating the prevalence of unilateral IMC uptake (tumour uptake with no visualization of the contralateral adrenal gland) and bilateral uptake (uptake in both the tumoral and the contralateral adrenal glands) in patients with unilateral incidentaloma. Comparison of adrenocortical function and of IMC scan after dexamethasone (DXM) in the two scintigraphic groups thus defined.
  
  
  METHODS
  Thirty-five patients with a unilateral mass highly suggestive of benign adrenocortical adenoma on CT scan.
  
  
  METHODS
  The IMC scan was performed in basal conditions (baseline scan) and after DXM (suppression scan). Adrenocortical function assessment included basal measurements of 11-deoxycortisol, 17 alpha-hydroxyprogesterone (17-OHP), dehydroepiandrosterone sulphate (DHEAS), plasma cortisol and ACTH, urinary free cortisol (UFC), overnight and low-dose DXM suppression test, and CRH test.
  
  
  RESULTS
  The baseline scan showed 16 patients (46%) with unilateral uptake (group A) and 19 (54%) with bilateral uptake (group B). Patients in group A exhibited lower ACTH values at 0800h (P = 0.05) and higher cortisol values after an overnight DXM suppression test (P = 0.02), than did patients in group B. In addition, 3 patients in group A failed the overnight and the low-dose DXM suppression tests. Adrenal masses were larger in group A than group B (P = 0.04) and an inverse correlation was found in the whole population between tumour size and ACTH value at 0800h (P = 0.05). On the suppression scan performed in 14 patients (7 in each group), patients in group A continued to exhibit unilateral tumour uptake and bilateral uptake was suppressed in 72% of patients in group B. An adrenal mass was removed in 3 patients of group A with confirmed benign adrenocortical adenomas. In the post-surgical period, the contralateral gland was again visualized in a baseline scan and the hormonal evaluation returned to the normal range.
  
  
  CONCLUSIONS
  Unilateral 131I-6 beta-iodomethylnorcholesterol tumour uptake is a frequent feature in benign adrenocortical adenomas. Hormonal data and scintigraphic profiles obtained after dexamethasone, as well as hormonoscintigraphic changes observed after surgery, provide evidence that unilateral uptake is related to functioning adenomas with various degrees of autononomy and suggest that the 131I-6 beta-iodomethylnorcholesterol scan could be a valuable tool for screening 'subclinical' Cushing's adenomas.
authors: Service de Médecine Nucléaire, Centre François Baclesse, Caen, France.
authors: S
authors: S
authors: Bardet
authors: V
authors: V
authors: Rohmer
authors: A
authors: A
authors: Murat
authors: C
authors: C
authors: Guillemot
authors: R
authors: R
authors: Maréchaud
authors: M
authors: M
authors: Chupin
authors: P
authors: P
authors: Lecomte
authors: D
authors: D
authors: Simon
authors: B
authors: B
authors: Delemer
authors: S
authors: S
authors: Schneebelli
authors: D
authors: D
authors: Beutter
authors: V
authors: V
authors: Jacquin
authors: P
authors: P
authors: Peltier
authors: B
authors: B
authors: Charbonnel
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging* / Q000503:physiopathology; D000301:Adosterol; D000302:Adrenal Cortex / Q000378:metabolism / Q000503:physiopathology; D000306:Adrenal Cortex Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000368:Aged; D003346:Corticotropin-Releasing Hormone; D003907:Dexamethasone; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011877:Radionuclide Imaging
chemical_list: D007457:Iodine Radioisotopes; D000301:Adosterol; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone