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Unexpected factors affecting the sex of the baby
Last reviewed: 01.07.2025
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Researchers from the University of Geneva have sought to shed light on this complex process by identifying the crucial role of insulin and the insulin-like growth factors IGF1 and IGF2, a family of hormones known for their direct involvement in human metabolism and growth.
Researchers from the University of Geneva have sought to shed light on this complex process by identifying the crucial role of insulin and the insulin-like growth factors IGF1 and IGF2, a family of hormones known for their direct involvement in human metabolism and growth.
The absence of these factors at the time of sex determination makes it impossible to determine whether the embryo is male or female.
Insulin-like growth factors IGF1 and IGF2 are the most important representatives of the family of insulin-like growth factors. This family carries out autocrine, endocrine and paracrine regulation of growth processes, development and differentiation of cells and tissues of the body.
The results of this study, published in the scientific journal PLoS Genetics, allow for a better understanding of the process of sexual development and ultimately improve the diagnosis and practice of genetic counseling for individuals with disorders of sexual development.
In mammals, sexual development is a long process that begins at conception, when the transfer of X and Y chromosomes via sperm determines the sex of the embryo.
The researchers were interested in the role of the insulin-like growth factor family and their receptors in cells.
These factors are known to be involved in the regulation of metabolism and growth, and also play a key role in the regulation of human reproductive capacity, whether male or female. Reproductive function is, in fact, closely related to metabolism and growth.
In fact, this makes perfect sense: a person cannot develop normally without sufficient energy intake, and there is no point in reproducing if caloric intake is insufficient. This may explain why some women with anorexia have anovulatory cycles and may suffer from infertility.
Obese people have significant fertility problems. Although it is now known that the interactions between metabolism, growth and reproductive capacity are regulated by common factors such as insulin and insulin-like growth factors, research by Professor Serge Nef of the Department of Genetic Medicine shows that these interactions are even more important than previously thought, since insulin and insulin-like growth factors are also important for primary sex determination in mammals.
To analyze the influence of these factors on sex determination, Professor Nef's group used genetically modified mice. The scientists genetically inactivated receptors for insulin and insulin-like growth factors in mouse embryos.
They found that due to the absence of these factors at the time of sex determination, the failure of gonadal colonization in these mutant mice prevented the embryos from developing testes or ovaries. Thus, the embryo and its gonads remained in an undifferentiated state for several days, demonstrating the essential role of these hormones and growth factors in sexual differentiation.