Double-isotope derivative assay of serum lodothyronines: II. Thyroxine

✍ Scribed by Garrett A. Hagen; Lincoln I. Diuguid; Bernard Kliman; John B. Stanbury

• Book ID: 102983945
• Publisher: Elsevier Science
• Year: 1970
• Tongue: English
• Weight: 678 KB
• Volume: 38
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(70)90477-x

✦ Synopsis

Because determination

of serum protein bound iodine (PBI) or butanolextractable iodine (BEI) is not specific for circulating thyroxine (T4), other means of quantitation of the hormone are being developed. These include (1) competitive protein binding analysis (l-4), (2) iodine determination following thin-layer or column chromatography or solvent distribution

(5-S), (3) gas chromatography with electron capture detection (9-11)) and (4) double-isotope derivative formation (12-13).

In the double-isotope derivative procedure unknown T4 is labeled by formation of an acetyl derivative using tritium-labeled acetic anhydride. The derivative is purified and counted for tritium activity. If the specific activity of the tritiated derivative is known, the T4 content of the sample can be calculated. Because the purification results in loss, a known amount of T4 labeled with radioactive iodine is introduced at the beginning of the procedure. This isotope is counted simultaneously with tritium at the end and a correction made for loss. The specific activity of the 1311-labeled compound is high enough so that its contribution to the assay value is negligible.

Whitehead and Beale reported success with ,a double-isotope derivative