MilliporeSigma, Billerica, Mass, has introduced the first certified spiking solution of intact, heavy-labeled thyroglobulin (Tg) in SigMatrix, a synthetic surrogate serum. The matrix-based reference material is suitable as an internal standard for the quantification of Tg levels by liquid chromatography-tandem mass spectrometry methods to ensure accurate, identifiable, and quantifiable clinical diagnostic testing. MilliporeSigma’s solution-based product is the first endogenous protein biomarker of the extensive Cerilliant portfolio. Measurement of patient Tg levels is performed primarily to monitor differentiated thyroid carcinoma recurrence following therapy, and is useful in determining the cause of hyperthyroidism and for monitoring treatment effectiveness in Graves disease. Quantitative mass spectrometry-based analysis of Tg concentrations in serum is the preferred assay for measuring Tg in Tg antibody-positive patients. For more information, visit MilliporeSigma.