Androgens are required for maintenance of spermatogenesis and for stimulation of the accessory glands. The peripheral androgen concentration is determined mainly by the steroidogenic activities of Leydig cells which are regulated by luteinizing hormone (LH), other hormones and also by locally produced factors. The androgen level in the testis is also, therefore, under the influence of LH. Since Leydig cells are the source of androgens, much higher levels are present in the testis than in peripheral androgen-dependent organs. There has been a long-running debate as to whether this high intratesticular concentration of androgen is essential for maintenance of spermatogenesis, or whether it is a prerequisite for the secretion of androgens. It has been suggested that locally produced factors operate to keep intratesticular testosterone levels high, especially in between LH pulses or at those specific stages of spermatogenesis which require high testosterone levels (Sharpe, 1984, 1986). Support for this hypothesis was