Rat testis membranes possess insulin receptor whose autoregulation is different from conventional insulin target organs. In order to verify the importance of the functional activity of the Leydig cells, different approaches were selected to provoke a resting state of the cells and to measure insulin binding. Testosterone cypionate and LH-RH agonist administration, as well as hypophysectomy, led to a 50% decrease of insulin binding in testis while no effect or a slight increase was observed in hepatic membranes following hypophysectomy. HCG treatments restored insulin binding to its control levels in hypophysectomized animals. These modifications occurred without significant changes in insulin and glucose concentrations. It is concluded that pituitary LH is a key factor in controlling Leydig cell activity as well as its insulin receptor content.