131I-Adosterol (Norcholesterol)

Overview

¹³¹I-Adosterol, also known as ¹³¹I-6-iodomethylnorcholesterol, 6-β-iodomethyl-19-nor-cholest-5(10)-en-3-β-ol, ¹³¹I-NP-59, or NCL-6-131I, is a radiolabeled cholesterol derivative commonly used in the diagnosis and investigation of adrenocortical disorders. Occasionally, it is mistakenly referred to as ¹³¹I-Aldosterol. This specialized compound plays a vital role in medical imaging, particularly in adrenal gland assessments.

Clinical Applications

The primary application of ¹³¹I-Adosterol is in adrenal scintigraphy, a diagnostic imaging technique used to detect and localize adrenal abnormalities. Its key use lies in evaluating adrenal cortical lesions, such as adrenal adenomas, and investigating incidental adrenal masses or cases of hyperaldosteronism.

While ¹³¹I-Adosterol is particularly effective for these conditions, its role in diagnosing Cushing’s syndrome is limited. Cushing’s syndrome, typically caused by bilateral adrenal hyperplasia, does not benefit significantly from this imaging tracer due to its specificity.

Patients undergoing an ¹³¹I-Adosterol examination typically receive a dosage of approximately 1 mCi.

Availability

¹³¹I-Adosterol is produced by a few specialized manufacturers, including Fuji-Film (Adosterol-131) and IBA Molecular (Curium) under the trade name Norchol-131 (EU MA 2003). Its availability is restricted to a limited number of European countries and Japan due to regulatory approvals.

Market and Competition

The market for ¹³¹I-Adosterol is niche, with limited demand and competition. Despite its specific use case, ¹³¹I-MIBG is generally the preferred tracer for adrenal imaging, given its broader applicability and established efficacy.

Future Considerations

¹³¹I-Adosterol is recognized as a highly specific diagnostic agent, making it valuable when more generalized imaging techniques fail to provide precise information. However, its future in medical practice may be uncertain. Advancements in imaging technologies and the integration of in vitro diagnostic methods are likely to reduce its use. Over time, this tracer may be phased out in favor of these emerging alternatives.