Since the earliest days of endocrinology, hormones have been imagined as something to titrate and to tinker with; to measure and also to inject or swallow. The founding story of sex endocrinology famously figures French physiologist Charles Brown-Séquard injecting himself with a preparation of crushed guinea-pig or dog testicles to rejuvenate his declining sexuality. Sex hormones, in particular, have always led a twin-track existence—conceived of both as natural actors in essential life processes of development and differentiation and as something to intervene in and with. As “messengers of sex” (Roberts 2007), hormones have been understood to act outside human intention and intervention and to be hugely important to the physiology of sex, even as they have been extracted from the bodies of human and nonhuman animals and/or artificially replicated to deliberately intervene in these processes.

In the 1920s, Dutch science studies scholar Nelly Oudshoorn (1994, 108) argues, “sex hormones could best be described as drugs looking for a market.” By the 1960s, markets were already well established: in human and veterinary medicine; in the production of meat; and in some sports, notably bodybuilding. Sex hormones were promoted as solutions to a range of challenging problems including conception and contraception, menopause and andropause, underdeveloped musculature in human and nonhuman animals, and menstrual pain and gender transition. In the 1980s, the development of IVF and related technologies of artificial fertilization in agriculture increased the mass use of hormones to stimulate ovulation in the hope of controlling reproduction.

In the later decades of the twentieth century, concerns about safety dogged many of these projects: worries about increased rates of violent behavior in men taking steroids in sport; troubling findings that the daughters of women who took diethylstilbestrol (DES) to avoid miscarriage were at increased risk of vaginal cancer; and concerns that hormone replacement therapies seemed to cause long-term harm to some aging women. Late twentieth-century environmentalist movements, for their part, highlighted the potentially harmful actions of hormones (and chemicals that mimic their actions) in food, water, furnishings, and ubiquitous objects such as plastic bottles and toys.

Today, as colleagues have beautifully articulated in the preceding posts, we remain caught in this dual figuration of hormones as natural and necessary, on the one hand, and as something in which to intervene, on the other. Hormones of various kinds are entering a widening set of arenas of daily life, including parenting, sport, and the workplace. In both the United Kingdom and the United States, for example, adoptive parents are trained to decode the behavioral signs of the flows of stress hormones in the family and to come to recognize and intervene in the long-term hormonal legacies of early-life trauma (Mackenzie and Roberts 2017). In some countries, puberty-blocking treatments are offered to pubescent children who are developing “too early” or in ways they do not want (that is, in ways that confirm a sexed embodiment with which they do not identify; see Roberts 2015). Sex hormones are also widely available in unregulated online markets for people with sufficient means who want to experiment with their sexuality and/or sex/gender (Preciado 2013). Visual artists are also increasingly working with hormones, both to document and creatively analyze such life projects and to explore directly what hormones can do in art (when applied to film surfaces, for example). Examples include the work of artists in the Queering Love, Queering Hormones project and the Transitional States: Hormones at the Crossroads of Art and Science exhibition.

Additionally, hormones are—like many other aspects of life—rapidly becoming something to track and record. Cheap ovulation-monitoring devices can be bought over the counter to track the ebb and flow of progesterone in one’s saliva at home (Wilkinson, Roberts, and Mort 2017). More expensive devices, requiring users to send saliva samples off to a laboratory, measure the levels of the so-called stress hormone cortisol. Linked to a wide range of negative health outcomes, particularly when a person experiences what are considered atypical patterns for a long time, cortisol is tricky to measure because it fluctuates regularly across the day, such that one-off testing is unlikely to be particularly informative. Longer-term cortisol patterns can, however, be measured in hair strands, opening up options to track these hormones over months in relatively painless ways (Roberts and McWade n.d.). Tracking cortisol is said to be potentially helpful to athletes in training, workers in high-stress competitive jobs, and foster carers trying to help young children (Van Andel et al. 2014).

The use of biosensing or self-tracking devices constitutes an important part of a growing cultural emphasis on knowing, and thus knowingly intervening into, hormonal flows. As the preceding posts argue, we cannot always control how hormones or their mimics enter or work within our bodies, but we can increasingly track these movements and, in sometimes surprising ways, be held responsible for at least trying to manage them. The parents of traumatized children, for example, are encouraged by psychologists to try to “optimize their children’s cortisol levels” in order to “help their brain work better” (Purvis, Cross, and Sunshine 2007, 53) and to behave in less disturbing ways. The tracking of hormones thus opens up new avenues of intervention, whereby one might tinker with one’s life in order to change hormonal flows rather than working directly on or with hormones. The parents of a child with elevated cortisol, for example, might learn to modulate their voice or massage their child, rather than looking for pharmaceutical solutions.

Viewed historically, hormones provide a fascinating lens though which to understand how bodies are enacted across diverse cultures. As material-semiotic actors they cut across boundaries of nation-states, sex/gender, social class, and species, but nonetheless are always geographically and historically specific in their messaging actions. Used critically as research tools, biosensing devices may give us insights into such diversities, allowing us to trace and analyze these boundary-crossing flows. In multiple ways, then, hormonal flows constitute political sites and rich zones for engaged analysis and experimentation.