The physiological institute of the University Tübinge has succeeded in preventing vascular calcification in Klotho-deficient mice by inhibiting osteogenic signal transduction. The animals reach an almost normal life span despite increased 1.25 (OH) 2D3, Ca2 + and phosphate plasma concentrations. The male animals are again fertilized, but not the female animals. However, if the plasma concentrations of 1.25 (OH) 2D3 are normalized by administration of a vitamin-poor diet, the female animals are fertilized within two weeks. Further investigations revealed an inhibitory effect of 1.25 (OH) 2D3 on the implantation of the embryo. In the meantime the 1,25 (OH) 2D3-dependent signal transduction could be revealed, which prevents the implantation of the embryo. The vitamin D receptor and the elements of signal transduction are also expressed in the human endometrium. It is therefore possible that increased 1.25 (OH) 2D3 plasma concentrations also prevent embryo implantation in humans.