Veterinar, Vol. 64 No. 1, 2026.
Professional paper
https://doi.org/ISSN 0303-5409
Science Without Gender Bias: Why We Need Both Males and Females
Doroteja Hunjadi
*
Mirna Mandić
; Department of Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, University of Zagreb
Mirela Pavić Vulinović
; Department of Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, University of Zagreb
* Corresponding author.
Abstract
Gender differences and sexual dimorphism in anatomical, histological and physiological foundations
are currently a major topic within the scientific community. Despite well-known differences between sexes,
males have traditionally been used as the standard research subjects, largely due to their relatively stable
hormonal profiles compared to females. Due to the female hormonal cycle, studies often need to be conducted
across multiple phases of the cycle, which requires additional time and financial resources. This has
been one of the primary reasons for the historical bias towards male specimens. It is now recognized that
merely including both sexes in research is not sufficient; it is also necessary to investigate the mechanisms
underlying sex-related differences across various aspects of biomedical research. In females, the follicular
and luteal phases of the reproductive cycle are regulated by complex hormonal interactions between gonadotropic
hormones and gonadal steroid hormones. In contrast, the male reproductive cycle is relatively
simpler, with spermatogenesis serving as the primary process regulated by gonadotropic hormones. These
differences may influence both research outcomes and methodological approach. Sex determination is
governed by a small number of genes, yet their activation leads to the expression of thousands of other
sex-specific genes. In fields such as toxicology, immunology, microbiology and oncology, differences have
been documented in xenobiotic metabolism, the strength of immune responses, susceptibility to infections,
and responses to antitumor therapies. Neuroscientific studies also show differences in the activation of
brain centres involved in the regulation of behaviour, emotions, memory, and stress. All of the above highlights
the necessity of systematically including individuals of both sexes in scientific research. Such an
approach represents a key prerequisite for a more comprehensive understanding of the biology of animal
organisms, the pathological processes that affect them, and the role of sexual dimorphism in shaping research
design and implementation, as well as in the interpretation of the results obtained.
Keywords
sexual dimorphism; hormonal cycle; biomedical research; animal models
Hrčak ID:
348979
URI
Publication date:
8.7.2026.
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