Serum tetraiodothyroacetate (T4A) levels in normal healthy euthyroid individuals determined by gas chromatography-mass fragmentography (GC-MF).

A gas chromatography-mass fragmentography (GC-MF) assay for T4A in human serum is described. The assay involves a multistage extraction, followed by conversion of T4A to its dimethyl derivative prior to GC-MF. Using this assay, the concentration of T4A in 37 normal euthyroid subjects was, mean +/- S.D., 114.5 +/- 26.4 pmol/l, which is considerably lower than previous reports. Thyroxine binding prealbumin (TBPA) did not appear to be a major determinant of T4A concentration.