Outside of pregnancy, the uterus usually does not receive much time under medical fire. No more! Scientists are beginning to explore the complex relationship between the uterus, ovaries and the brain to better understand the impact of removal of these organs on a person's health.
Rats whose uterus was removed have more difficulties with working memory than rats that have undergone other types of gynecological operations, discovered a study published this week in the newspaper. Endocrinology. The scientists behind the research claim that it is a first step in analyzing how the reproductive system – and the decisions to modify it – can influence cognition and health.
Until recently, the medical community primarily considered the uterus as a "baby home," says Donna Korol, a biologist who studies the neural mechanisms of learning and memory at the University of New York. Syracuse and who did not participate in the new study. But given the role of the organ in the production and regulation of hormones, this is gradually starting to change.
"In general, the dogma on the ground is that the non-pregnant uterus is dormant – some experts have termed it". useless, "said co-author of the study, Heather Bimonte-Nelson, neuroscientist of behavior at Arizona State University. "We think that a woman's reproductive organs might have a higher value than their reproductive capacity, so we wanted to further evaluate the effects of the uterus."
In the United States, about one-third of women undergo hysterectomy before the age of 60, and the majority of them before the natural age of menopause around the age of 50 years. This is the second largest surgical procedure among women in the United States after cesarean section. section. And in about half of these surgeries, the uterus will simply be removed from the patient, while in the other half, the uterus and ovaries will be removed. The retention of the ovaries can prevent a woman from entering a sudden and early menopause after the surgery. Ovarian removal may also be associated with an increased risk of heart disease and osteoporosis.
Previous studies have shown that estrogen and other hormones produced by the ovaries can help protect nerve structures in the brain while improving cardiovascular, cutaneous, bone and urogenital health. But the uterus and ovaries are closely linked and the nerves connect the brain to these two reproductive organs. Some studies have begun to look more closely at this relationship, assessing the relationship between hysterectomy and the risk of early dementia. "We're just starting to look at the uterus as a regulator of brain function instead of focusing on the ovaries," says Korol.
Bimonte-Nelson and Stephanie Koebele, a graduate student in the Bimonte-Nelson lab and co-author of the paper, began the experiment by performing surgery on 60 rats. A group of rats has just removed their uterus (a hysterectomy), another group has just removed their ovaries (an oopherectomy), a third group is receiving the uterus and ovaries, and a fourth and last group is undergoing surgery but no organ. The researchers used procedures that mimic the types of surgeries performed on humans.
The rats recovered from their operation for six weeks before Koebele and Bimonte-Nelson put them to the test. The researchers evaluated the spatial memory and working memory of each rodent using a series of labyrinths that forced rats to find platforms submerged in water and return to these platforms, where they were. Koebele and Bimonte-Nelson wanted to assess the rats' ability to recall navigation cues and modifications made by labyrinth researchers during the experiment.
They found that the group of rats from which only the uterus had been removed was worse off in the labyrinth designed to test the working memory than the others. Working memory is like a short-term memory that needs to be updated, explained Bimonte-Nelson. For example, simply recalling a phone number is an example of short-term memory. The fact of having to memorize this telephone number, then to manipulate it in one way or another, for example by adding the numbers, requires a working memory.
About two months after the operation, the scientists re-examined the rats that still had their ovaries. They found that if the physical structure of the ovaries did not change, the hormonal balance in the hysterectomy group and in the group in which no organ was taken was slightly different, which indicates that removing only the uterus would result in slight ovarian production. different hormones – at least for a short time after surgery.
Bimonte-Nelson and Koebele were not so surprised that this group was so different from the group where the uterus and ovaries had been removed. The difference, says Bimonte-Nelson, is that simply removing the uterus disrupts the neuro-ovarian-uterine connection instead of completely removing that system. When the system is disrupted, the remaining organs will try to resume play to return to normal, potentially resulting in the hormonal changes observed by scientists in the hysterectomy group.
The short delay – only two months after surgery – means that scientists can not draw conclusions about the long-term effects of hysterectomy on cognitive function. It is also a study on animal model, the results will not be precisely correlated with what happens in humans. Even in this case, research from this group represents the vanguard of efforts to better understand menopause, Korol said.
Much remains to be learned, but one thing is clear: it is time for the uterus to obtain credit that exceeds its baby capacity.