Endocrine Regulation of Seasonal Reproductive Physiology

Seasonal breeders synchronise reproductive activity with favourable environmental conditions by integrating external cues, chiefly photoperiod, with internal endocrine pathways. Changes in day length are transduced by the pineal hormone melatonin, which modulates hypothalamic pulse generators for gonadotrophin-releasing hormone (GnRH). Pulsatile GnRH regulates pituitary secretion of luteinising hormone (LH) and follicle-stimulating hormone (FSH), driving gonadal steroidogenesis and gametogenesis. Prolactin additionally acts on reproductive tissues such as the gonads and accessory glands to fine-tune seasonal physiology. At the cellular level, seasonal shifts in steroid hormone receptors, local growth factors and non-coding RNAs orchestrate morphological and functional changes in testes, ovaries and secondary sexual structures. Comparative studies in rodents, ungulates and other vertebrates reveal conserved neuroendocrine circuits, with species-specific adaptations. Insights into these mechanisms are critical for wildlife conservation, optimising breeding in agricultural species and predicting reproductive responses to climate-driven shifts in seasonality.

Research from Nature Portfolio

Recent studies have demonstrated that prolactin receptor expression in accessory scent glands of male rodents varies markedly between breeding and non-breeding seasons. During the reproductive phase, glandular and interstitial cells display elevated receptor density and mRNA abundance, accompanied by increased circulating prolactin. Concurrent profiling of microRNAs reveals season-dependent regulatory networks that target prolactin-responsive genes, suggesting a direct paracrine role for prolactin in modulating gland function. These findings establish non-gonadal tissues as dynamic targets of seasonal endocrine signals and highlight microRNA-mediated control as a novel layer in reproductive timing.

Endocrine Regulation of Seasonal Reproductive Physiology publication trend

The graph below shows the total number of articles in endocrine regulation of seasonal reproductive physiology across all publications each year (not limited to Nature Index journals).

Technical terms

Photoperiodism: The physiological response of organisms to the relative lengths of day and night.

Melatonin: A pineal hormone secreted in darkness that conveys photoperiodic information to the neuroendocrine axis.

Hypothalamic–pituitary–gonadal axis: The hierarchical endocrine pathway linking GnRH secretion, pituitary gonadotrophin release and gonadal steroidogenesis.

Prolactin: A pituitary peptide hormone with roles in lactation, reproductive tissue regulation and seasonal breeding.

Androgen receptor: A nuclear receptor that mediates the actions of testosterone and other androgens on target cells.

MicroRNA: Small non-coding RNAs that post-transcriptionally regulate gene expression and contribute to seasonal tissue remodelling.

References

1. Seasonal Expression of Prolactin Receptor in the Scented Gland of Male Muskrat (Ondatra zibethicus). Scientific Reports (2015).
2. Mass Spectrometry Imaging of Lipids in the Scent Glands of Muskrat (Ondatra zibethicus) in Different Reproductive Statuses. Cells (2022).
3. Musk gland seasonal development and musk secretion are regulated by the testis in muskrat (Ondatra zibethicus). Biological Research (2017).
4. Prolactin inhibitor changes testosterone production, testicular morphology, and related genes expression in cashmere goats. Frontiers in Veterinary Science (2023).