Somatic tissue responses of male rhesus monkeys treated with a contraceptive steroid formulation

Abstract Rhesus monkeys ( Macaca mulatta ) were treated with testosterone (100 μg/kg/day) plus estradiol (0.5 μ/kg/day) via subcutaneous polydimethylsiloxane (PDS; Silastic) implants for thirteen months. This steroid regimen inhibited dramatically spermatogenesis. Gross and histopathological examination of the musculoskeletal, circulatory, endocrine (excluding the testis), central nervous, gastrointestinal and respiratory systems failed to uncover any untoward effects of the long-term exposure due to the contraceptive formulation. Similarly, no remarkable effects were observed in the ionic, chemical and formed elements of blood or secondary sex structures. Failure to detect secondary complications attributed to the steroid treatment offers further justification for evaluating a contraceptive strategy based on administering naturally occurring steroids at sustained rates approximating those at which they are produced endogenously in the human male.