Paracrine factors relevant to the regulation of spermatogenesis - a review

Introduction In the last two decades, it has become increasingly evident that disturbances of the hypothalamic–pituitary–gonadal axis account for only a small percentage of the cases seen in male infertility clinics. In an attempt to clarify the pathophysiology of idiopathic male infertility and also for the development of new methods for male contraception, researchers have focused on local regulators of intratesticular events (Bartlett et al., 1989; Hamilton and Waites, 1989). The number of factors implicated in paracrine regulation has been steadily increasing and it is essential that the data available are critically examined. The object of this review is to pinpoint the factors of potential or proven physiological significance and to concentrate on the more recent advances made in the field. The two major areas of activity within the testis centre on steroidogenesis and spermatogenesis. The intratesticular control of steroidogenesis has already been extensively reviewed (Sharpe, 1990) and this paper