Nav: Home

Researchers are finding molecular mechanisms behind women's biological clock

October 09, 2019

Researchers have mapped out some of the mechanisms that may affect women's fertility from the teenage years to menopause. These mechanisms largely depend on naturally occurring chromosome errors - errors that vary depending on age group.

This is the conclusion by an international research group in a new study, led by researchers from the University of Copenhagen. The scientists, who come from a number of European universities, have reached their conclusion after examining 3000 egg cells from girls and women between the ages of nine and 43.

'We have known for a long time that we humans have a unique fertility curve compared to many other species. The curve starts out very poorly in the teenage years and starts to go downhill again when women reach their 30s. But until now, we have not known what is actually causing these changes', says Head of Research and Professor Eva Hoffmann from the Department of Cellular and Molecular Medicine at the University of Copenhagen.

Molecular Glue

Unlike men who do not form sperm until they reach puberty, women are born with all the egg cells they will have available throughout life. However, the eggs are immature and do not fully develop until the menstrual cycle begins.

'While the eggs lie dormant, a kind of molecular glue will make the chromosomes stick together. Later, when the eggs are maturing, the chromosomes divide. But the older the women become, the greater the risk that the glue will break down prematurely', says Eva Hoffmann.

The hereditary material thus falls apart, resulting in chromosome errors which may, for example, lead to syndromes such as Down, Turner or Kleinfelter. Or which may make the eggs infertile.

Also in teenage girls, the researchers found a greater incidence of chromosome errors during the maturing of the eggs. In this case mostly due to the eggs not reaching a sufficient level of maturity.

This meant that in adolescence, especially the larger chromosomes in the hereditary material developed defects - and thus increased the likelihood that the eggs would be expelled by the body without being fertilized.

As the teens turned into young women, the researchers observed how the eggs became healthier, while the chromosome errors gradually disappeared. A trend that continued until the women were in their late 20s, after which other types of chromosome errors started to set in.

Wider Hips and Grandmothers

Scientists do not yet know for sure exactly why human fertility rises, peaks and falls within a defined age range. By comparison, our close fellow species, the chimpanzees, do not in the same way experience menopause, but are rather consistently fertile throughout their adult life.

According to Eva Hoffmann, it may be a matter of two evolutionarily developed mechanisms in humans. First, a mechanism that protects very young women from becoming pregnant until their bodies are fully developed - and thus better able to bear children due to, for example, wider hips that reduce the risks associated with giving birth.

Second, a mechanism that potentially makes older women take on a new, supportive role as grandmothers when their own children become able to produce offspring - a theory which within a number of research fields has become known as the 'grandmother hypothesis'.

Eva Hoffmann points out that the new results may be used to improve the dissemination of information about child-bearing and pregnancy loss. Just as the increased knowledge may be able to improve the treatment of infertility in the long term.

'Pregnancy loss is still a taboo, but with knowledge like this, we are able to better understand and demonstrate that it is a natural thing. At the same time, a greater understanding of the mechanisms behind our biological clock may enable us to better control the breakdown of the eggs. Either in the eggs themselves or in the maturation process in the fertility clinic', says Eva Hoffmann.
-end-


University of Copenhagen The Faculty of Health and Medical Sciences

Related Fertility Articles:

Fertility preservation use among transgender adolescents
Transgender adolescents often seek hormonal intervention to achieve a body consistent with their gender identity and those interventions affect reproductive function.
A new way to assess male fertility
Current tests for male fertility include measuring the concentration and motility of spermatozoa.
Male fertility after chemotherapy: New questions raised
Professor Delbès, who specializes in reproductive toxicology, conducted a pilot study in collaboration with oncologists and fertility specialists from the McGill University Health Centre (MUHC) on a cohort of 13 patients, all survivors of pediatric leukemia and lymphoma.
Vaping may harm fertility in young women
E-cigarette usage may impair fertility and pregnancy outcomes, according to a mouse study published in the Journal of the Endocrine Society.
Are fertility apps useful?
Researchers at EPFL and Stanford have carried out an analysis of the largest datasets from fertility awareness apps.
Marijuana and fertility: Five things to know
For patients who smoke marijuana and their physicians, 'Five things to know about ... marijuana and fertility' provides useful information for people who may want to conceive.
How could a changing climate affect human fertility?
Human adaptation to climate change may include changes in fertility, according to a new study by an international group of researchers.
Migrants face a trade-off between status and fertility
Researchers from the universities of Helsinki, Turku and Missouri as well as the Family Federation of Finland present the first results from a new, extraordinarily comprehensive population-wide dataset that details the lives of over 160,000 World War II evacuees in terms of integration.
Phthalates may impair fertility in female mice
A phthalate found in many plastic and personal care products may decrease fertility in female mice, a new study found.
Climate change damaging male fertility
Climate change could pose a threat to male fertility -- according to new research from the University of East Anglia.
More Fertility News and Fertility Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Clint Smith
The killing of George Floyd by a police officer has sparked massive protests nationwide. This hour, writer and scholar Clint Smith reflects on this moment, through conversation, letters, and poetry.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.