Development and Characterization of Silicone-Based Testosterone Propionate Implants for Sustained Androgen Delivery in Juvenile Castrated Male Pigs

Validated techniques for androgen replacement in swine research models are limited, particularly for studies requiring controlled hormone delivery in males during early development. We adapted a silicone-based androgen implant methodology originally developed for adult female pigs to establish an androgen replacement model in castrated juvenile male pigs. • Castrated male pigs were surgically implanted with low (0.5 g), medium (1.0 g), or high (2.0 g) doses of testosterone propionate (TP), and compared with castrated controls. • Intact male pigs were included as a physiologically relevant reference group to benchmark implant-derived testosterone concentrations against endogenous androgen production during juvenile development. • Circulating testosterone was monitored weekly for 49 days to evaluate the concentration and duration of testosterone release. • Body weights were recorded weekly to assess body weight gain. Testosterone propionate implants produced a dose-dependent elevation in circulating testosterone that peaked between 7 to 14 days post-implantation and reached or exceeded concentrations of intact males. Following peak release, testosterone levels gradually declined across all implant groups but remained elevated relative to castrated controls throughout the 49-day study period, with the medium- and high-dose groups maintaining the highest concentrations. Growth rates of animals were similar across experimental groups, indicating that TP implantation did not adversely affect overall growth during the study. These findings validate silicone-based TP surgical implants as a reliable method for sustained androgen delivery in juvenile, prepubertal pigs, establishing a tractable model for mechanistic studies of androgen action with translational relevance to human and animal health.