The transplantation of endocrine organs can be regarded as the oldest form of transplantation in modern medical history. By the end of the nineteenth and beginning of the twentieth centuries, a large research focus was set on endocrine transplantations. Before the complex endocrine secretion and function was even understood, researchers attempted to cure endocrine diseases and infertility through transplantation of the endocrine glands and gonads. Hence, most endocrine organs have been transplanted in that period, including the thyroid , the adrenal gland , the testis  and the ovary . Even though the principles of transplant rejection have not been understood at that time, researchers already noticed successful transplantations almost exclusively in experiments with autografts. The first published allogeneic ovarian transplantations in animals have been performed by Paul Bert in the sixties of the nineteenth century .