Houston, Texas, USA : By age 60, one in three American women have had a hysterectomy. Though hysterectomy is a prevalent and routine surgery, the removal of the uterus before natural menopause might actually be problematic for cognitive processes like memory.
Researchers in the Arizona State University Department of Psychology have found rats that underwent the surgical removal of the uterus with ovaries left intact had a memory deficit, suggesting the uterus might have functions beyond reproduction. The study will be published on December 6 in Endocrinology.
A dormant and useless organ?
Endocrinology textbooks used in medical and graduate schools describe the uterus as having the sole function of accommodating and supporting a fetus or as a useless organ outside of reproduction. But, there is mounting evidence from research in animals and people suggesting otherwise.
The uterus and ovaries communicate for reproductive functions, but there are also direct connections between the uterus and the brain through the body’s autonomic nervous system. The autonomic nervous system coordinates unconscious functions like breathing and digestion. The lesser understood uterine-brain connections could affect cognitive functions and impact how females age.
“There is some research showing that women who underwent hysterectomy but maintained their ovaries had an increased risk for dementia if the surgery occurred before natural menopause. This finding is striking,” said Heather Bimonte-Nelson, professor of psychology and senior author on the paper. “We wanted to investigate and understand whether the uterus itself could impact brain function.”
The research team used female rats to systematically test the role of the uterus and ovaries in learning and memory. The rats were divided into four groups based on the type of menopause surgical intervention. The three experimental groups were: removal of the uterus with ovaries left intact, removal of the ovaries with uterus left intact and removal of both the uterus and ovaries. The fourth group underwent a sham surgery in which no reproductive organs were removed.
Six weeks after surgery, the researchers taught the four groups of rats how to navigate a maze. Once all the rats had learned this task, the researchers tested the memory capacity of the rats. The team also looked at the reproductive organs and hormones.
“This experiment tests the role of the uterus in cognitive changes that accompany menopause. The researchers use several surgical approaches that are actually used for women who undergo oophorectomy, hysterectomy, or both. This alone is laudable,” said Donna Korol, an associate professor of biology at Syracuse University who was not part of the study. “One of the beauties of this experimental design was the sampling of different measures from the same rat, allowing for within-animal comparisons across multiple systems.”
A rodent version of the card game “concentration”
During the memory testing, the rats navigated a water maze that looked like a sunburst, with eight arms radiating out from a circular center. There were submerged platforms at the end of some of the arms, and the rats had to swim to locate a hidden platform. In the beginning of the experiment, the researchers placed four platforms for the rats to find. After a rat found a platform, the researcher removed it for the rest of the day. The rat then restarted the maze, searching for the remaining platforms while having to remember both where previous platforms had been and which arms had always been empty.
With two platforms down and two to go, the research team found the rats that had only the uterus removed could not handle the increased memory load. These rats kept returning to places where there had never been a platform, indicating they were unable to remember which arms of the maze led to platforms.
The other kinds of surgery did not affect how many mistakes the rats made in the maze. The rats that underwent the removal of just the ovaries or the removal of the ovaries plus the uterus navigated similar to the group that had the sham surgery.
“The surgical removal of just the uterus had a unique and negative effect on working memory, or how much information the rats were able to manage simultaneously, an effect we saw after the rats learned the rules of the maze” said Stephanie Koebele, ASU psychology graduate student and first author on the paper.
A hormonal jigsaw puzzle
At the end of the study, the researchers looked at the size, shape and structure of the ovaries in all the groups. The ovaries of the hysterectomy-only group were indistinguishable from the ovaries of the sham surgery group, which maintained their ovaries and uterus.
The research team also measured the amounts of different hormones in the blood, like progesterone, follicle-stimulating hormone and luteinizing hormone. Hormones are chemicals made by the body that regulate organs and body systems and send information. The hormone levels in the hysterectomy-only group were different from the sham surgery group, even though both of these groups still had ovaries.
“Even though the ovaries were structurally similar across all the groups, the hormones that were produced in the group that received hysterectomy alone resulted in a different hormone profile,” said Koebele, who has a fellowship from the National Institute on Aging for her doctoral research. “Hormones affect both brain and other body systems, and having an altered hormonal profile could impact the trajectory of cognitive aging and could create different health risks.”
Exactly how the altered hormone profile affects cognitive aging or creates health risks is complicated but is nonetheless very important to study and understand.
“Complicated does not mean impossible,” said Bimonte-Nelson, who directs ASU’s Behavioral Neuroscience of Memory and Aging lab. Her lab is currently testing whether the memory deficit after hysterectomy is reversible with time or is the beginning of a more global memory impairment.
Citation: “Hysterectomy Uniquely Impacts Spatial Memory in a Rat Model: A Role for the Nonpregnant Uterus in Cognitive Processes,” Endocrinology.
Video : The non-pregnant uterus is commonly assumed to be an unimportant organ. A third of American women have a hysterectomy by age 60, often before natural menopause. Arizona State University researchers have found an animal model of hysterectomy resulted in decreased memory capacity and an altered hormonal profile within two months after surgery. The study suggests an important role for the uterus that could impact cognitive aging.
Video and image credit: Robert Ewing, ASU
A second study concluded that egg-preserving hysterectomy raises heart risks later
Egg-preserving hysterectomy raises heart risks later
Women who undergo hysterectomy before age 35 may face significantly higher long-term heart risks, even if their ovaries are preserved, a new study found.
The research by experts at Mayo Clinic focused on more than 2,000 US women who had their uterus removed but left their ovaries intact—widely considered the most desirable option if possible because it prevents a woman from entering early menopause.
Compared to women in the same area of Minnesota who did not have hysterectomies, the study found those who did faced a greater risk of obesity, clogged arteries, high blood pressure and high cholesterol in the 20-plus years after surgery.
The elevated risks ranged from 13 percent more for high blood pressure to 33 percent more for coronary artery disease.
For women under age 35, the risks were particularly acute—a 4.6-fold increased risk of congestive heart failure and a 2.5-fold greater risk of coronary artery disease, when the arteries become hard and narrow, blocking blood flow.
“This is the best data to date that shows women undergoing hysterectomy have a risk of long-term disease—even when both ovaries are conserved,” said lead author Shannon Laughlin-Tommaso, an obstetrician-gynecologist at Mayo Clinic.
“Hysterectomy is the second most common gynecologic surgery, and most are done for benign reasons, because most physicians believe that this surgery has minimal long-term risks,” she added.
Some 400,000 operations to remove the uterus, or womb, are performed each year in the United States.
Most are not due to life-threatening conditions like cancer, but rather because of painful fibroids, menstrual disorders or uterine prolapse, when the uterus begins to sag into the vagina, according to the study.
In cases of cancer or high genetic risks, doctors may remove the uterus, fallopian tubes and ovaries. In other cases, just the uterus is taken out, rendering a woman unable to become pregnant but preserving her hormonal function through the ovaries, thereby postponing menopause.
This option became more popular after research showed that removing the ovaries along with the uterus can raise the risk of early death and chronic disease.
But experts say the effects of ovary-preserving hysterectomies have not been well studied until now.
“While women are increasingly aware that removing their ovaries poses health risks, this study suggests hysterectomy alone has risks, especially for women who undergo hysterectomy prior to age 35,” said Laughlin-Tommaso.
“With the results of this study, we encourage people to consider nonsurgical alternative therapies for fibroids, endometriosis and prolapse, which are leading causes of hysterectomy.”
According to obstetrician-gynecologist Jill Rabin, who was not involved in the study, the research is “well-powered” and “fascinating.”
While the biological reasons for the health risks are still being studied, researchers suggested that the uterus may play a role in communicating with the hormone-producing ovaries.
Therefore, removing the womb may cut blood flow and change hormonal stimulation to the ovaries, leading to negative effects on the entire body.
“It makes perfect sense if you think about it. It’s all connected. Once you disconnect it, it is like cutting a telephone line in a way. You are stopping the communication,” said Rabin, who is co-chief of the division of ambulatory care and women’s health programs at Northwell Health in New York.
Hysterectomy can also be a life-saving operation, depending on the reason, so women who are considering it should consult closely with their doctors, she added.
“It should be decided with your doctor, spelling out the risks and benefits, so the patient really understands.”
Since the study was observational in nature, it stops short of proving cause-and-effect, but raises interesting questions for further research, according to Mitchell Kramer, chairman of the department of obstetrics and gynecology at Huntington Hospital in New York.
In the meantime, any women thinking about the surgery “should consider alternatives to hysterectomy,” including treatment with medicines or less invasive procedures, he said.
The study was published in the journal Menopause.