In recent years, mandates from funding agencies and scientific journals have driven a significant increase in the number of biomedical researchers incorporating sex- and gender-related considerations into our work (Haverfield and Tannenbaum, 2021; Institute of Gender and Health, 2023; Potluri et al., 2017; Rechlin et al., 2022; Woitowich et al., 2020). The most obvious approach to doing so (and one that is explicitly encouraged by some of these mandates) is to use both female and male participants, animals, tissues, or cells in the design of experiments and studies (Clayton, 2016; Clayton and Collins, 2014; Klein et al., 2015). At the same time, some scholars have noted that this is not always as simple as it may first appear, and can lead to problematic analyses and conclusions (Eliot, 2011; Maney and Rich-Edwards, 2023; Rich-Edwards et al., 2018; Ritz, 2017; Ritz et al., 2014). Although inclusion of female and male subjects and the female-male comparisons that are often done in these contexts can lead to useful insights to inform our understanding of the impact of gender/sex-related factors on health, the mere inclusion or comparison of females and males will ultimately be inadequate for making significant inroads in addressing gender inequities in health. This is because the categories of female and male themselves are imperfect proxies for the material sex- and gender-related factors that mechanistically produce most observed sex and gender differences. Simply put, these binary categories lack the complexity both within each category and between categories to adequately model factors related to gender/sex that influence health.

When we start to push past the female-male binary itself and begin to consider what specific mechanisms might mediate the influences of gender and sex, one of the first candidates that jumps to mind for many biomedical scientists is hormones – especially estrogens, androgens, and progestogens. Indeed, there is little doubt that these hormones, along with the larger suite of other hormones associated with gender and sex (HAGS),1 contribute to the emergence of many sex- and gender-associated differences reported in a wide range of physiological processes and health outcomes. Investigating the contribution of HAGS to biomedical questions will undoubtedly enhance our scientific understanding and our ability to intervene clinically where HAGS are mechanistically implicated. Scientists whose specific expertise is in hormones and behaviour will likely be aware of the misconceptions about hormones due to cultural gender stereotypes, and have a deep appreciation of the intricacies of hormone-mediated pathways and regulation. Individuals new to this field (including biomedical researchers examining HAGS principally as a way to address funding and publishing mandates on gender/sex considerations) may not be as attuned to these kinds of nuances.

As biomedical science has taken up the mandates to include sex and gender considerations in research, the distinction between sex and gender is often summarized with the shorthand that sex is biological, while gender is social. This is a useful starting point for distinguishing between sex and gender, but can become a problematic over-simplification in a variety of ways (Ritz and Greaves, 2022; Springer et al., 2012; van Anders and Watson, 2006). We are reticent to offer our own definitions of sex and gender here, not only because a plethora of definitions have already been offered, but also because these definitions continue to evolve, and because the context will determine which aspects are most salient. For the present purposes, we will principally rely on the provisional definitions offered by Ritz and Greaves (2022), where:

Sex refers to the biological attributes and functions associated with anisogamy such as chromosomal complement, endocrine function, reproductive and sexual anatomy, secondary sex characteristics, and other physiological and morphological variations and processes not directly related to reproduction (such as body size and composition, metabolic function, or organ function).

Gender refers to aspects of social organization that shape the range of roles, norms, behaviors, relations, aesthetics, and activities that are culturally determined to be related to presumptively belonging in a sex category. Gender encompasses the norms, roles, and institutional structures that shape any individual’s experiences, exposures, and access to power and resources, as well as one’s sense of self as a gendered individual.

Although the concepts themselves are distinct from one another, in practice we usually find that sex and gender are deeply entangled. Like the classic nature-vs-nurture debate, it is not usually a question of one or the other, but more often it is both together in dynamic interaction. In recognition of this entanglement, we often employ the hybrid term gender/sex to indicate that both are at play. With respect to HAGS specifically, the term gender/sex can serve as an important reminder that although hormones are biological substances, their expression can be profoundly affected by social, environmental, and behavioral stimuli, which will be discussed in more detail below.

Here we will explore three key issues to consider when investigating the impact of HAGS in biomedical research that we hope will be particularly helpful for biomedical scientists whose principal expertise is not in hormones. First, we will discuss how the discourses commonly employed in the discussion of HAGS profoundly shape our scientific thinking due to social and cultural stereotypes, and how bringing a critical lens to these discourses can improve our scientific practice. Second, we will discuss how the mechanistic relationships between HAGS and observed gender/sex differences in biomedical phenomena are more complex and dynamic than they are often presumed to be, with implications for our hypothesis generation, experimental design, and interpretation of findings. Finally, we will conclude by offering some guidance for biomedical researchers who aim to address questions related to HAGS as part of our efforts to address sex and gender considerations.