Animals Have a Sex, and so Should Titles and Methods Sections of Articles in Endocrinology

Beginning with papers submitted as of July 1, 2012, the methods sections of manuscripts submitted to Endocrinology must indicate the sex of animals used, or in the case of primary cells or cultures, the sex of animal from which they were derived. Although not required, authors are also encouraged to identify the sex of cell lines used in cell cultures. If the experiment is of a mixed-sex design, the numbers of males and females should be indicated in the methods. If only one sex of animal was used in an experiment, the title should indicate the sex of animal used. Recently, the Institute of Medicine of the National Academies of Science recently hosted a workshop entitled “Sex-Specific Reporting of Scientific Research” sponsored by the Office of Research on Women’s Health of the National Institutes of Health (1). The opinion of many of the discussants was that, considering the differences between males and females for so many biological factors, the sex of animals used in experiments should be identified in journal articles. Similarly, most participants agreed that when only one sex was studied, then that should be clearly indicated in the methods section of the paper. This issue of Endocrinology includes three invited minireviews that persuasively make the case that the sex of animals is a critical variable in all of biology (2–4). These three minireviews note the importance of knowing the sex of the animals used in studies ranging from immune cells to human brain function. Although the study of only one sex is acceptable in some cases, such as reproduction, the study of only one sex with an expectation of generalizing to both sexes is not. With many variables, the response of males and females may differ as much as in studies in which different strains or species of animal are used. Therefore, we believe it is of utmost importance to prominently identify the sex of animals used in biological research. Although experiments will continue to be performed on only one sex, it is important to call attention of our authors and readers to this issue. In addition to the Institute of Medicine monograph on sex-specific reporting of scientific research and the minireviews in this issue of Endocrinology, many other publications recently have made the case that sex cannot be ignored in biological research (5, 6). Beery and Zucker (5) conducted an extensive analysis of sex of animals used in publications in a variety of disciplines. In some disciplines, when sex of animal is specified in the methods sections of scientific reports, the subjects tend to be males, perhaps because researchers do not want to deal with the so-called complication of the estrous or menstrual cycle of females. It is interesting that 20 yr ago, Karen Berkley (7) pointed out that in many research papers, in that case, in Neuroscience, the sex of animals used was not specified. We expect that our new policy will evolve as awareness of the need to consider both sexes in endocrine research increases, and we expect that just as was the case in human research, the federal agencies will get involved in the conversation. In time, inclusion of both sexes in animal research may be required, as it is now with human subject studies (http://orwh.od.nih.gov/inclusion.html). Eventually, sex-specific information may be required in studies with a mixed-sex design. However, for now, our goal is to raise awareness of the fact that, just as species, strain, age, and other variables must be considered in reporting of biological research, so should sex of animals. Although some recent papers have provided blueprints of how to consider both sexes in biological research (8, 9), the goal of the new policy of this journal is simply to ensure that the sex of animals is reported and mentioned in the title if only one sex was used. The goal is not to change the