For all those who believed benefit of boosting ideal with the GH rhu produced by genetic engineering, it must be remembered that the isoform 20 is absent from this exogenous hormone, probably due to the manufacturing technique. However it is this isoform which allows the best adaptation to the exercise of endurance: it is lipolytique and hyperglycaemic activity. With the advancement of science and 10 years after, it is therefore, not surprised that Alex Zülle, the cyclist Switzerland of the Festina, had not found effective its cure of GH! Once again, the GH gives us the example that use such a product with as little certainties, is to play the role of the sorcerer's apprentice. We also understand why some studies concluded that the non-effectiveness of the GH in the endurance training.