Abstract
A sensitive fluorimetric method using p-cresol as a hydrogen-donating substrate is described for th assay of thyroid peroxidase in a crude preparation of human thyroid tissue. The fluorescence of the product formed enzymatically from p-cresol is measured at 410 nm with excitation at 325 nm in an alkaline solution (pH 12.3). The specific activities of thyroid peroxidase are 2 to 5 times higher in tissues from patients with Graves' disease than in normal tissues from patients with adenoma of the thyroid. This method is simple and sensitive enough to allow the enzyme assay to be carried out with as little as 10 mg of thyroid tissue.