Laboratory issues in the implementation of the marker method

Two important biomarkers for the identification of growth hormone or IGF-I administration are IGF-I and P-III-P. These substances are determined in plasma or preferably in serum. There are a number of assays on the market for IGF-I but only two for P-III-P. The principles behind these assays and the choice of assays for doping control purposes are discussed. The future possibility of quantification by mass spectrometry is also briefly discussed.