Researchers have uncovered a new link between chronic stress and reproductive problems, in a pre-clinical study that shines the spotlight on a hunger-triggering hormone.
The study suggests high levels of the hormone ghrelin, which stimulates appetite and is also released during stress, could be harmful to some aspects of reproductive function.
Researchers at RMIT University found that by blocking the ghrelin receptor in female mice, they were able to reduce the negative effect of chronic stress on a key aspect of ovarian function.
Senior co-author Dr Luba Sominsky said the study, published in the Journal of Endocrinology, showed the need for further research on the long-term impact of chronic stress on fertility and the role of ghrelin in regulating these effects.
But the current findings could have implications for those with underlying fertility issues, Sominsky said.
"Stress is an inseparable part of our lives, and most of us deal with it quite efficiently, without major health problems," she said.
"This means young and otherwise healthy women may experience only temporary and probably reversible effects of stress on their reproductive function.
"But for women already suffering from fertility problems, even a minor impact on their ovarian function may influence the chance and timing of conception."
Sominsky, a Vice-Chancellor's Postdoctoral Research Fellow at RMIT, said that although this work is exclusively in mice, there are many similarities to humans in stress responses, as well as in many phases of reproductive development and function.
"Our findings help clarify the intriguing role of ghrelin in these complex connections, and point us on a path towards future research that could help us find ways of mitigating the effects of stress on reproductive function."
Associate Professor Sarah Spencer, senior co-author on the study, said the study indicated there could be a relationship between eating, stress and reproductive function.
"Because ghrelin is so closely linked to hunger and feeding, these findings very broadly suggest that our eating habits may be able to modify the effects of stress on fertility, although we need to do more work to fully assess this," Spencer said.
The 'hunger hormone' and reproductive health
Ghrelin is a metabolic hormone that triggers feelings of hunger, increases food intake and promotes fat storage.
It's also released when we are stressed; ghrelin is part of the reason we want to eat when we feel emotional or under pressure.
Neuroscientists at RMIT have been exploring the role of ghrelin in healthy reproductive function, and implications for fertility.
In this new pre-clinical animal study, they investigated how ghrelin may mediate the effects of chronic stress on the ovarian primordial follicle reserve.
Female mammals are born with a fixed number of these "immature" follicles, which do not regenerate or regrow if they are damaged.
While the majority of primordial follicles will die and never complete their development, a small proportion will eventually develop further to become preovulatory follicles.
This means the fewer "immature" ones you have, the fewer "mature" follicles later in life that can release an egg cell for fertilisation.
The study found that female mice exposed to chronic stress had significantly fewer primordial follicles.
But when the researchers blocked the effect of ghrelin on its receptor, they found the number of primordial follicles was normal - despite the exposure to stress.
"The length of the female reproductive lifespan is strongly linked to the number of primordial follicles in the ovary," Sominsky said.
"Losing some of those primordial follicles early on is often predictive of earlier reproductive decline and deterioration.
"This research is in early stages, with many steps to go before we can translate this clinically.
"But getting a better understanding of the role of ghrelin in all of this brings us an important step closer to developing interventions that can keep these critical parts of the reproductive system healthy."
The study was conducted by researchers in the Neuroendocrinology of the Obese Brain Research Group, in the School of Health and Biomedical Sciences at RMIT.
Question: What is the hunger-triggering hormone?
Dr Luba Sominksy: The hunger-triggering hormone, ghrelin, is released from the stomach and the gut. It signals to our brain to start eating when we are hungry. This hormone also plays role in other functions of our body, like those we've focused on in our research: stress and reproductive function.
Question: How can we manage this hunger-triggering hormone?
Dr Luba Sominksy: The release of this hormone is a natural and important occurrence, which helps us to efficiently manage our appetite and other important functions.
Question: How does stress and this hormone affect our reproductive system?
Dr Luba Sominksy: We still have a lot of work to do to establish the link between these three factors. So far, we know that this hormone, ghrelin, is also released in response to stress. While acutely (in the short term) this release is beneficial and it helps our brain and body to manage stressful situations, when stress becomes chronic, a continuous increase in the levels of this hormone may have negative effects on some aspects of our health.
Question: In what ways can we manage this hormone?
Dr Luba Sominksy: What is really important is to manage our life stress, so this and other physiological outcomes of stress are not affecting our wellbeing. There are many ways to do that. For instance, maintaining healthy social relationships, exercising regularly and eating healthy are all effective strategies in managing stress and these activities have positive influence on our health.
Question: How would you define chronic stress?
Dr Luba Sominksy: Stress is very subjective. The source of chronic stress can be an unpleasant work environment, an unsatisfactory personal life, being stuck in traffic every day on the way to and from work and many other situations that some people can find more stressful than others.
Question: Does chronic stress only affect the reproductive system of females?
Dr Luba Sominksy: It is important to remember that the link between stress and reproductive system is very complex. What some of us find stressful, others do not, and while some of us can be susceptible to stress, others may be better in managing it. Therefore, being stressed is not necessarily going to affect your reproductive system, whether you are a male or a female.
Question: What's the main message we can take from this study?
Dr Luba Sominksy: In many cases, the effects of stress on our health are reversible, including the negative effects of stress on reproductive system that we saw in our study. Therefore, being able to manage stress and engage in all those healthy activities I mentioned above can have a very positive impact on our life and wellbeing.
Interview by Brooke Hunter