Physiologic role and regulation of intratesticular sex steroids.

PURPOSE OF REVIEW

To summarize recent advances in our understanding of the role and regulation of intratesticular androgens, and their metabolites, in human spermatogenesis.

RECENT FINDINGS

Over the last few years, a number of studies have been published examining intratesticular sex steroid concentrations in normal men following gonadotropin manipulation and in the setting of impaired fertility. Advances in the field have been facilitated by the availability of more sensitive and specific assays for intratesticular sex steroid quantification. High levels of intratesticular androgens are required for normal spermatogenesis in men. However, the quantitative relationship between intratesticular testosterone concentrations and male fertility is not fully understood. In the setting of impaired spermatogenesis, intratesticular metabolites of testosterone may play a role in initiating or maintaining fertility.

SUMMARY

Advances in the precision of androgen measurements and recent studies examining intratesticular responses to hormonal manipulation have advanced our understanding of the testicular microenvironment. These advances have set the stage for future studies in this area which will be important for moving forward male hormonal contraceptive development and furthering our understanding of male reproductive pathology. Whether 'gonadotropin-independent' intratesticular androgen synthesis plays a role in human spermatogenesis will likely be a focus of investigation in the coming years.