Functional scintigraphy of the adrenal gland

Abstract

Over the last 30 years nuclear medicine imaging of the adrenal gland and its lesions has been achieved by the exploitation of a number of physiological characteristics of this organ. By seeking and utilising features which are quantitatively or qualitatively different from those of the adjacent tissues, functional depiction of the adrenal gland and its diseases, which in most cases retain the basic physiology of their tissue of origin, including both the cortex and the medulla, are now a useful clinical reality. Agents widely used in clinical practice include: (a) uptake and storage of radiolabelled cholesterol analogues via the low density lipoprotein (LDL) receptor and cholesterol ester storage pool in the adrenal cortex ( 131 I-6-b-iodomethyl-norcholesterol, 75 Se-selenomethyl-norcholesterol); (b) catecholamine type I, presynaptic, uptake mechanism and intracellular granule uptake and storage mechanism in the adrenal medulla and extra-adrenal paraganglia ( 131 I-, 123 I-and 124 Imeta-iodo-benzyl-guanidine (MIBG), 18 F-metafluoro-benzyl-guanidine); (c) cell surface receptor binding of peptides/neurotransmitters/modulators such as for the family of five subtypes of somatostatin receptors ( 123 I-tyr-octreotide, 111 In-DTPA-octreotide, 111 In-DOTA-octreotide and many others); (d) although not specific for the adrenal gland, increased glycolysis by tumours, particularly the most malignant varieties, 18 F-2-fluoro-D-deoxyglucose can thus be expected to depict certain malignant lesions such as malignant pheochromocytomas (particularly the minority which are not detected by MIBG) and adrenal incidentalomas (particularly when they occur in patients with known extraadrenal malignancies). There are a variety of adrenal tissue characteristics with potential for exploitation but which are not currently in clinical use, and which may, nevertheless, have potential as imaging agents. These include: (a) inhibitors of adrenal cortical steroid hormone synthesis enzymes (e.g. radiolabelled analogues of metyrapone); (b) radiolabelled lipoproteins which bind to adrenocortical LDL receptors; (c) inhibitors of catecholamine biosynthesis enzymes (e.g. radiolabelled analogues of tyrosine and related amino acids); (d) cell surface receptors for various peptides and hormones which may be overexpressed on adrenal cortical or adrenal medullary tumours (e.g. radiolabelled analogues of ACTH on adrenocortical cells of zona fasciculata or zona glomerulosa origin, neurotransmitter/hormone message peptides binding to cell surface receptors such as bombesin, vasoactive intestinal polypeptide, cholecystokinin and opiate peptides); (e) the adrenal cortex can also synthesise cholesterol ab initio from acetate, and preliminary studies with 11 C-acetate positron emission tomography have shown interesting results. European Journal of Endocrinology 147 13-28 Adrenal cortexThe adrenal cortex is constituted of three layers. The outer layer, the glomerulosa zone, produces mineralocorticoids (mainly aldosterone) under the control of the renin -a...

AME Position Statement on adrenal incidentaloma

“…In previous studies, two radiocholesterol derivatives have mainly been studied: 131 I-6-b-iodomethyl-norcholesterol (NP-59) and 75 Se-selenomethyl-19-norcholesterol for morphological and functional imaging of adrenal cortex (48). A disadvantage with the radiotracers is their inherent high radiation dose (49).…”

An exceedingly rare adrenal collision tumor: adrenal adenoma–metastatic breast cancer–myelolipoma

“…Studies have demonstrated the high sensitivity (94–100%) and specificity (80–100%) of FDG-PET in differentiating benign and malignant adrenal lesions [10,11]. Adrenal radiocholesterol scintigraphy is also considered to be very accurate in distinguishing benign adrenal adenomas from extra-adrenal lesions [12]. …”

Androgenproduzierende Tumoren

“…In den vergangenen Jahren ist es mög-lich geworden, auch kleinste endokrin aktive Tumoren der NNR aufgrund ihrer Tumorbiologie mithilfe spezifischer radioaktiv markierter Tracer in der Szintigraphie zu detektieren [14]. Die NNR exprimiert Low-density-Lipoprotein-Rezeptoren, welche durch markiertes Cholesterin sichtbar gemacht werden können.…”

“…Die NNR exprimiert Low-density-Lipoprotein-Rezeptoren, welche durch markiertes Cholesterin sichtbar gemacht werden können. Der aktuell für die Norcholesterinszintigraphie gängige Radiotracer ist I-6-β-Iodomethylnorcholesterin (NCL-6-I) [14]. Mitunter ist eine genaue Lokalisationsdiagnostik jedoch auch unter Einsatz moderner, bildgebender tumorspezifischer Verfahren und selektiver Venenkatheterisierung nicht möglich.…”

“…Im Zuge des Hyperandrogenismus, der auf einen ektopen Androgenexzess zurückzuführen ist, entwickelt sich häufig konsekutiv das klinische Bild eines PCOS[29,30].Da die Bildung von Glukokortikoiden, Mineralokortikoiden und Androgenen in der NNR über verschiedene Prohormone miteinander verknüpft ist, kann es beispielsweise beim Morbus Cushing neben der exzessiven Glukokortikoidbildung auch zu einer vermehrten Produktion von Androgenen kommen. Die Androgenbildung in der NNR unterliegt der Regulation durch die Hypothalamus-Hypophysen-NNR-Achse[14]. Pathologische Veränderungen in übergeordneten endokrinen Zentren, die sich auf die Gonadotropinsekretion auswirken, resultieren in Stö-rungen der Hormonsekretion.…”