Maternal blood iron level: For the first time, an external factor turns a male mammal into a female

[cbabe]

https://english.elpais.com/science-tech/2025-06-04/for-the-first-time-an-external-factor-turns-a-male-mammal-into-a-female.html

For the first time, an external factor turns a male mammal into a female

An experiment in mice has discovered that a mother’s iron deficiency alters sex determination. Until now, it was believed that only genetics defined this biological trait

NUÑO DOMÍNGUEZ
JUN 04, 2025 - 12:39 EDT

All living people have been both male and female at the same time for six weeks. Although our sex is determined at the moment the sperm fertilizes the egg, it is not until a month and a half later that the biological programming to develop testes or ovaries is activated.

Textbooks have always taught that this process is 100% dictated by genetics: males have one female and one male chromosome, XY, and females have two female chromosomes, XX. But on Wednesday, the results of a bold experiment with mice were published, showing that very low iron levels in the mother can transform males into females, regardless of their genetics.

“To our knowledge, this is the first demonstration that an environmental factor can influence sex determination in a mammal,” Makoto Tachibana, a biologist at Osaka University in Japan and leader of the research, published in the journal Nature, tells EL PAÍS. “The most important implication of this finding,” he adds, “is that environmental and metabolic conditions influence fundamental developmental decisions that until now were thought to be strictly determined by genetics.”

… more …

[SARose]

1. Well my my my

The researchers discovered that if iron concentration is reduced by 60% at the cellular level, the testicular gene is switched off. When they reproduced this iron deficiency in pregnant female mice carrying males, they observed that six out of 39 XY offspring were born with two ovaries, a complete sex reversal. Another mouse was born intersex, with one ovary and one testicle.

From the article above. Emphasis mine.

[Bernardo de La Paz]

2. Perhaps the root of gender dysphoria: male genes, female body?

If this goes one way, there might be another deficiency or surplus that goes the other way: female genes, male body.

[Wicked Blue]

4. I have long suspected that environmental chemicals such as phthalates

play a role in gender dysphoria. Phthalates are just about everywhere in our environment now, and can cause serious endocrine disruption.

[erronis]

3. Fascinating. To think that everything is not always black or white!

De colores!

[Javaman]

5. coming soon to your nearest right wing eugenics center. nt

[k_buddy762]

6. Cool in mice

but what about in humans?