Suppression of spermatogenesis to azoospermia by combined administration of GnRH antagonist and 19-nortestosterone cannot be maintained by this non-aromatizable androgen alone

H.M. Behre1,2, S. Kliesch1, B. Lemcke1, S. von Eckardstein1 and E. Nieschlag1,3 1 Institute of Reproductive Medicine of the University (WHO Collaborating Centre for Research in Human Reproduction), D-48129 Münster, Germany