A major international study into the role cortisol plays in reproduction has found it may not be the villain it has been depicted as, and it may actually promote healthy reproduction.
The large systematic review, led by Australia's La Trobe University and involving scientists in the United States and Canada, found that while cortisol is often labelled a “stress hormone”, they are a normal and potentially supportive part of female reproductive cycles.
Researchers reviewed almost 70 studies into cortisol across the animal kingdom, including mammals, birds, reptiles, amphibians and fish, searching for information about normal cortisol patterns across the ovarian cycle.
They found that 73 per cent of the studies reported a significant change in cortisol during healthy ovarian cycles, with levels often increasing around the time of ovulation, suggesting it is a normal part of healthy female ovarian cycles.
The findings have been published in the Journal of Experimental Biology .
Senior author Dr Kerry Fanson, the Head of Wildlife Conservation and Reproductive Endocrinology Lab at La Trobe University, said the findings challenged the simple view that elevated cortisol levels always suppressed reproduction – and in fact suggested they are an important part of fertility.
“Infertility is a huge issue across the spectrum, not just for humans - it’s important for people like dairy farmers who want to know why their cows aren’t getting pregnant, or for helping support the survival of endangered species,” she said.
“While our study didn’t include humans, our findings relate to people as the principles are the same.”
Dr Fanson said the findings meant reproductive scientists could now factor natural cortisol into fertility studies and support better outcomes.
“Our study suggests we’ve been oversimplifying the role cortisol plays in fertility. Imagine trying to treat diabetes if you didn’t think insulin was involved. By recognising that cortisol plays an important role in reproduction, it creates new opportunities to diagnose and treat reproductive problems,” she said.
The study was jointly led with Assistant Professor Phoebe Edwards from the Department of Ecology, Evolution, and Organismal Biology at Iowa State University, with collaboration from Gabriela Mastromonaco from Reproductive Sciences at Toronto Zoo.
Read the full report here: Increases in glucocorticoids are part of healthy female ovarian cycles: a systematic review across vertebrates | Journal of Experimental Biology | The Company of Biologists
DOI: doi.org/10.1242/jeb.252436
Journal of Experimental Biology
Systematic review
Not applicable
Increases in glucocorticoids are part of healthy female ovarian cycles: a systematic review across vertebrates Icon for The Forest of Biologists
12-Oct-2026