Maternal Hormones in Avian Development

Maternal hormones deposited in avian eggs constitute a pivotal mechanism by which mothers influence offspring phenotype before hatching. These non-genetic factors include steroid hormones such as androgens and glucocorticoids, and iodinated compounds known as thyroid hormones. Deposited in the yolk, these molecules regulate gene expression, cell proliferation and differentiation in embryonic tissues, shaping neurodevelopment, metabolism, growth trajectories and stress responsiveness. Maternal allocation of hormones may vary with laying order, environmental conditions and maternal condition, yielding fine-tuned adjustments to ecological challenges. Embryos exhibit a degree of metabolic plasticity, modulating hormone uptake and conversion via yolk-sac transporters and deiodinase enzymes, which can lead to mother–offspring conflicts over optimal hormone levels. Across taxa, variation in hormone deposition has been linked to sibling hierarchies, brood reduction strategies and post-hatch survival. Investigating these maternal effects enriches our understanding of avian life-history evolution and offers practical insights for conservation, poultry science and the management of wild bird populations under changing environmental pressures.

Research from Nature Portfolio

Recent studies have explored the plasticity of embryonic metabolism in response to maternal androgens. Experimental elevation of androstenedione and testosterone in early eggs revealed that embryos adjust the rate of hormone metabolism according to laying sequence and initial yolk concentration, demonstrating embryo-driven modulation of maternal signals. This plasticity may mitigate potential mother–offspring conflicts and contributes to flexible developmental trajectories. Another investigation characterised the proteomic landscape of egg albumen and yolk in a model passerine, showing that egg composition varies systematically with laying order and maternal age. Proteomic variation was functionally biased among eggs, indicating both passive deposition and active compensatory mechanisms. These findings underscore the dynamic interplay between maternal allocation and embryonic processing, highlighting intricate biochemical environments that underlie early avian development.

Maternal Hormones in Avian Development publication trend

The graph below shows the total number of articles in maternal hormones in avian development across all publications each year (not limited to Nature Index journals).

Technical terms

Androgens: Steroid hormones, such as testosterone, deposited in the egg yolk that influence growth, competitive behaviour and muscle development in embryos.

Glucocorticoids: Stress-related steroid hormones, including corticosterone, that modulate energy metabolism, immune function and developmental plasticity when transferred maternally.

Thyroid hormones: Iodinated compounds (T3 and T4) essential for coordinated gene expression, tissue differentiation and neural maturation prior to endogenous thyroid activity.

Maternal effects: Non-genetic influences by which maternal phenotype, condition or environment alters offspring development via resources or signals in the egg.

Developmental plasticity: The capacity of the embryo to adjust physiological or morphological trajectories in response to maternal signals and environmental cues.

References

1. Plasticity in metabolism of maternal androgens in avian embryos. Scientific Reports (2023).
2. The Role of Maternal Thyroid Hormones in Avian Embryonic Development. Frontiers in Endocrinology (2019).
3. Life history shapes variation in egg composition in the blue tit Cyanistes caeruleus. Communications Biology (2019).
4. Developmental plasticity of mitochondrial aerobic metabolism, growth and survival by prenatal glucocorticoids and thyroid hormones: an experimental test in wild great tits. Journal of Experimental Biology (2022).