However, the use of the Tfm model to delineate the role of AR in Leydig cells is complicated both by the effects of the absence of AR in other cells in the testis and the hypothalamic-pituitary-gonadal axis, and also the impacts of cryptorchidism associated with the Tfm mutant, which leads to temperature-induced degenerative effects (23). The gene discussed is AR; the disease is cryptorchidism.