Sexual Modulation of Testosterone: Insights for Humans from Across Species

Testosterone (T) is generally understood to influence sexual behavior, but how T responds to sexuality is less well characterized across vertebrate species. Here, we review and synthesize findings on sexual modulation of T in primates (including humans), birds, fish, and rodents, with attention to the specific elements of sexual situations that drive T responses. We use a comparative perspective to show how research with females and males from a wide distribution of taxa provides novel insights for understanding effects of sexuality on T in humans. Among other patterns, our cross-species synthesis highlights a) the importance of the context surrounding a sexual interaction, over and above specific sensory modalities, to sexual modulation of T; b) that changes in T and changes in sexual behavior or arousal do not always occur in concert; c) that sexual contextsmay be especially likely to increase T when coupled with aggression or competition, but sexuality contributes to T profiles independently as well; and d) that variation in T responses may be adaptive in balancing behavioral and physiological costs and benefits of T. We discuss how broadening the ways sexuality is defined, and especially decoupling sexuality from reproduction, would further clarify predictors and potential functions of sexually-modulated T. Overall, effects of sexuality on Tacross species highlight themalleability of androgens, particularly in response to the social environment. Not only does sexual behavior affect T, but the social environment in turn modulates the extent of sexuality's effect on T.