[The reign of hormones and the construction of gender differences].

Within the context of the theoretical debate on gender and science, the article discusses the process of redefining gender and sex differences using so-called biological or natural markers. It identifies how gender differences undergo naturalization using a logic of 'substantialization or 'materialization'. This process is exemplified in how medicine views women, promoting explanatory models of economics of the female body that are at times centered around organs like the uterus and ovaries, at other times centered on the mechanics of hormones, and, most recently, focused on genetic and neurological differences. More specifically, it follows the discovery of so-called sex hormones and its relation to a dualist perspective of gender. These powerful chemical messengers helped shaped the passage from the logic of excess surrounding sex through the late nineteenth century, to the imperative of insufficiency, prevalent since the mid-twentieth century.