Ovariectomy, the surgical removal of one or both ovaries, is one of the most commonly performed gynecological procedures worldwide and one of the most routine surgeries in veterinary medicine. In humans it is usually called oophorectomy, and when combined with removal of the fallopian tubes it becomes a bilateral salpingo-oophorectomy (BSO). The reasons for performing it range from cancer prevention to treatment of endometriosis to routine spaying of pets. What makes ovariectomy medically fascinating and sometimes controversial is the cascade of consequences that follow: removing the ovaries eliminates the body’s main source of estrogen, testosterone, and progesterone, setting off changes in nearly every organ system. Those downstream effects, and how they differ depending on species, sex, age, and whether hormone replacement is used, are the subject of ongoing research and real clinical debate.
Why Ovariectomy Is Performed in Humans
The most clear-cut indication for prophylactic ovary removal in otherwise healthy women involves inherited mutations in the BRCA1 or BRCA2 genes, which dramatically raise the lifetime risk of both breast and ovarian cancer. Bilateral salpingo-oophorectomy is considered the most effective strategy to reduce that risk.1PubMed Central. Risk-Reducing Bilateral Salpingo-Oophorectomy for BRCA Mutation Carriers and Hormonal Replacement Therapy: If It Should Rain, Better a Drizzle than a Storm A landmark study found that prophylactic oophorectomy in BRCA carriers cut the risk of ovarian and related cancers by roughly 96 percent and reduced breast cancer incidence by about half compared with women who kept their ovaries.2PubMed. Prophylactic Oophorectomy in Carriers of BRCA1 or BRCA2 Mutations Research focused specifically on BRCA1 carriers confirmed a similar breast cancer risk reduction, with the protective effect persisting and even strengthening over a decade or more of follow-up.3JNCI: Journal of the National Cancer Institute. Breast Cancer Risk After Bilateral Prophylactic Oophorectomy in BRCA1 Mutation Carriers
Beyond cancer genetics, ovariectomy is performed to treat conditions such as severe endometriosis, ovarian cysts, ovarian torsion, and certain hormone-receptor-positive cancers where removing the hormone source is part of the treatment plan. It is also sometimes done during hysterectomy for benign disease, a practice that has become more controversial as the long-term consequences of ovary removal have come into sharper focus.
The Hormonal Cliff of Surgical Menopause
When both ovaries are removed before natural menopause, the result is an abrupt and complete loss of ovarian hormones rather than the slow, years-long decline that characterizes natural menopause.4PubMed. The surgical menopause This distinction matters because the body has no time to adjust. The adrenal glands continue producing small amounts of androgens, and fat tissue can convert some of those to estrogen, but these backup sources fall far short of what the ovaries had been providing. Hot flashes, night sweats, vaginal dryness, and sleep disruption tend to arrive faster and hit harder than in natural menopause. The severity is especially pronounced in younger women whose ovaries were still producing hormones at peak levels.
That sudden hormonal drop is the engine behind nearly every downstream consequence discussed below. Whether the topic is bones, heart, brain, or mood, the core issue is the same: the body evolved to operate with a certain hormonal environment, and removing it overnight triggers a remodeling process that touches almost every tissue.
Cardiovascular Risk
Estrogen has protective effects on blood vessels, and losing it prematurely raises the risk of heart disease. A large cohort study found that women who had both ovaries removed before age 45 experienced about a 44 percent increase in cardiovascular mortality compared with women who kept their ovaries. Among women in that age group who did not take estrogen therapy, the risk was even steeper, nearly doubling. Women who did receive estrogen replacement did not show the increased risk.5PubMed Central. Increased cardiovascular mortality following early bilateral oophorectomy This pattern, younger age at ovary removal plus no hormone replacement equals greater cardiovascular danger, has been one of the most consistent findings in the field.
What Happens to Bones
Estrogen slows the breakdown of bone by restraining the cells that resorb it and supporting the cells that build it. Once the ovaries are gone, this balance tips toward loss.6JAMA Network Open. Changes in Bone Mineral Density After Prophylactic Bilateral Salpingo-Oophorectomy in Carriers of a BRCA Mutation A prospective study of premenopausal women who had risk-reducing BSO measured what happened over the next two years: bone mineral density at the lumbar spine dropped by about 5 percent, and tibial bending stiffness fell by roughly 12 percent. In women who did not take hormone therapy, the losses were even sharper, reaching about 6 percent at the hip and femoral neck.7PubMed. Loss of bone density and bone strength following premenopausal risk-reducing bilateral salpingo-oophorectomy: a prospective controlled study (WHAM Study) Those are not small numbers for a two-year window. They suggest that without intervention, younger women who undergo ovariectomy face a significantly accelerated path toward osteoporosis.
Brain, Memory, and Dementia Risk
The brain is rich in estrogen receptors, and removing the ovaries at a young age appears to affect long-term cognitive health. A study of older women found that those who had undergone surgical menopause showed faster decline in global cognition, episodic memory, and semantic memory compared with women who had natural menopause. Earlier age at surgery was also linked to greater accumulation of Alzheimer’s-type brain pathology.8PubMed Central. Age at surgical menopause influences cognitive decline and Alzheimer pathology in older women
A systematic review and meta-analysis added more texture to this picture. Surgical menopause at any age was associated with faster decline in verbal memory, semantic memory, and processing speed. When the analysis was restricted to early surgical menopause, defined as removal of the ovaries at age 45 or younger, the risk of dementia was about 70 percent higher than in women who had not had the surgery.9PubMed. Surgical menopause in association with cognitive function and risk of dementia: A systematic review and meta-analysis The younger the woman at the time of surgery, the steeper the later cognitive trajectory tended to be. This finding has become one of the strongest arguments against routine ovary removal during hysterectomy for non-cancer conditions.
Mood and Psychological Impact
Depression and anxiety rates rise measurably after premenopausal ovariectomy. A prospective controlled study of women undergoing risk-reducing BSO found that clinically significant depressive symptoms roughly doubled at three months after surgery compared with a control group, and that elevation persisted out to twelve months. Anxiety symptoms nearly tripled at three months before gradually returning to baseline by a year. Women who had the surgery faced about a threefold higher risk of chronic depressive symptoms, even when they were using hormone therapy.10PubMed. What happens after menopause? (WHAM): A prospective controlled study of depression and anxiety up to 12 months after premenopausal risk-reducing bilateral salpingo-oophorectomy
The hormonal mechanism here likely involves estrogen’s influence on serotonin activity in the brain. Women with pre-existing psychological vulnerabilities appear to be at particular risk: ovariectomy can destabilize mood in people whose psychiatric history is already fragile, and the loss of both estrogen and androgens may compound the problem.11PubMed. Psychological consequences of surgical menopause The take-home point is that even in women who are making a medically well-justified decision, the psychological aftermath deserves proactive attention rather than an afterthought.
Sexual Function and Androgen Loss
The ovaries are a significant source of testosterone, not just estrogen. After bilateral ovariectomy, circulating androgen levels drop markedly in both premenopausal and postmenopausal women.12PubMed. Androgens in women before and after the menopause and post bilateral oophorectomy: clinical effects and indications for testosterone therapy Women who have had their ovaries removed report higher rates of decreased libido, diminished orgasmic response, and reduced overall sexual satisfaction compared with women who retained their ovaries through hysterectomy.13PubMed. Androgen deficiency in the oophorectomized woman
Testosterone replacement has shown promise in this population. Several randomized controlled trials found that transdermal testosterone patches produced meaningful improvement in sexual desire among postmenopausal women who had undergone bilateral oophorectomy.14PubMed. Androgens in women before and after the menopause and post bilateral oophorectomy: clinical effects and indications for testosterone therapy Despite this, testosterone therapy for women remains under-prescribed and not universally approved by regulatory agencies, leaving many women without access to a treatment that the evidence supports.
Metabolic Changes and Weight Gain
Anyone who has undergone ovariectomy, or cared for an animal that has, will notice weight changes. Loss of ovarian function increases susceptibility to obesity and shifts in body fat distribution. Research in both humans and animal models has consistently shown that the abrupt hormone deprivation caused by ovariectomy leads to increased body fatness, insulin resistance, and unfavorable cholesterol profiles.15PubMed Central. Association of bilateral oophorectomy and body fatness in a representative sample of US women Animal studies show that ovariectomized subjects gain fat mass and develop higher circulating leptin levels.16PubMed. Increased weight gain after ovariectomy is not a consequence of leptin resistance
The causes are not limited to estrogen loss alone. Follicle-stimulating hormone (FSH), which surges once the ovaries stop providing feedback to the pituitary, may play its own role in disrupting energy balance and tissue metabolism.17PubMed Central. Effects of follicle-stimulating hormone on energy balance and tissue metabolic health after loss of ovarian function The implication is that estrogen replacement alone may not fully prevent the metabolic shifts that follow ovariectomy, because some of those shifts are driven by hormones going up rather than hormones going down.
Long-Term Survival and the Case for Ovarian Conservation
For women without a high-risk genetic mutation, the all-cause mortality data make a strong case for keeping your ovaries if there is no medical reason to remove them. Over 28 years of follow-up in the Nurses’ Health Study, about 17 percent of women who had hysterectomy with bilateral oophorectomy died from all causes, compared with about 13 percent of women who conserved their ovaries. Oophorectomy did reduce ovarian cancer deaths, but at no age was it associated with lower all-cause mortality.18PubMed Central. Long-term Mortality Associated with Oophorectomy versus Ovarian Conservation in the Nurses’ Health Study An earlier analysis from the same cohort found increased risk of death from coronary heart disease, lung cancer, and all cancers combined after oophorectomy, estimating that for every 24 women who had both ovaries removed, at least one would die prematurely as a result.19PubMed Central. Ovarian Conservation at the Time of Hysterectomy and Long-Term Health Outcomes in the Nurses’ Health Study
These data have gradually shifted clinical practice. Decades ago, it was common for surgeons performing a hysterectomy for benign conditions to remove the ovaries “while they were in there” as a cancer-prevention measure. The evidence now suggests that for average-risk women, this trade-off is unfavorable. The protection against ovarian cancer does not offset the accumulated cardiovascular, skeletal, cognitive, and mortality costs. For BRCA carriers, the calculus is very different, and the cancer risk reduction is large enough to justify the hormonal consequences, ideally with prompt hormone therapy to mitigate them.
Hormone Therapy and the Timing Question
A recurring theme in the data is that hormone replacement therapy blunts or erases many of the negative consequences of ovariectomy, but only when started early. The so-called timing hypothesis holds that estrogen therapy initiated close to the onset of hormone deficiency and continued until the average age of natural menopause, around 51 or 52, significantly reduces most of the increased risks seen in untreated women.20PubMed Central. Hormone replacement therapy in young women with surgical primary ovarian insufficiency The cardiovascular data tell the same story: women who took estrogen after early oophorectomy did not show the elevated cardiovascular mortality that untreated women did.21PubMed Central. Increased cardiovascular mortality following early bilateral oophorectomy Breast cancer risk reduction in BRCA carriers was not negated by hormone replacement therapy use, which is reassuring for women who worry that taking hormones after prophylactic surgery would undo the benefit.22JNCI: Journal of the National Cancer Institute. Breast Cancer Risk After Bilateral Prophylactic Oophorectomy in BRCA1 Mutation Carriers
The caveat is that hormone therapy does not fix everything. The mood data from the WHAM study showed persistent depression even in women using hormone therapy, and whether it fully prevents cognitive decline remains uncertain. Still, the current consensus is that for women undergoing premenopausal oophorectomy, starting hormone replacement promptly and continuing it to the age of natural menopause is a critical part of managing the procedure’s consequences.
Ovariectomy in Veterinary Medicine
In dogs and cats, ovariectomy is the surgical basis of “spaying,” though the procedure often includes removal of the uterus as well (ovariohysterectomy). In Europe, ovariectomy alone, without removing the uterus, has long been the preferred technique for routine neutering of healthy dogs. A comparison of the two approaches found no significant differences in the incidence of urogenital problems between dogs who had ovariectomy alone and those who had ovariohysterectomy. The study concluded that there is no indication for removing the uterus during routine neutering in healthy dogs, and that ovariectomy should be considered the preferred procedure.23PubMed. Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches Pain outcomes are also similar between the two approaches.24PubMed Central. Comparison of intraoperative and postoperative pain during canine ovariohysterectomy and ovariectomy
Laparoscopic ovariectomy has become increasingly available in veterinary practice, and it offers concrete advantages. A study comparing two-portal laparoscopy with traditional open surgery in dogs found that the laparoscopic approach took roughly half the time, produced less blood loss, left much smaller scars, and resulted in fewer post-operative adhesions.25PubMed Central. Comparison between two portal laparoscopy and open surgery for ovariectomy in dogs
The Neutering Timing Debate in Dogs
One of the most active controversies in veterinary medicine concerns when, not whether, to spay or neuter. Research has complicated the once-simple advice to spay all dogs at six months. A study of Golden Retrievers found that early neutering (before one year of age) was associated with higher rates of joint disorders such as hip dysplasia and cranial cruciate ligament disease, as well as increased incidence of certain cancers including lymphosarcoma and hemangiosarcoma in females.26PubMed Central. Neutering dogs: effects on joint disorders and cancers in golden retrievers A follow-up comparing Golden Retrievers with Labrador Retrievers found that the joint and cancer effects were far more pronounced in the Golden Retrievers, suggesting that breed-specific factors play a large role.27PLOS ONE. Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers
A much larger study expanded this analysis to 35 breeds and found wide variation. Some breeds showed no increase in joint disorders or cancers at any neutering age, while others showed significant elevations that differed by sex and timing.28PubMed Central. Assisting Decision-Making on Age of Neutering for 35 Breeds of Dogs: Associated Joint Disorders, Cancers, and Urinary Incontinence The emerging practical advice is that the “right” age to spay or neuter depends on the breed and size of the dog. For large and giant breeds prone to joint problems, veterinarians are increasingly recommending waiting until skeletal maturity. For smaller breeds with lower joint and cancer risk, the traditional timeline may remain appropriate. An alternative approach, ovary-sparing spay (removing the uterus but leaving the ovaries), is being explored by some owners. A survey-based study found that longer exposure to gonadal hormones, regardless of whether the dog could still reproduce, was associated with reduced odds of general health problems and behavioral issues.29JAVMA. Vasectomy and ovary-sparing spay in dogs: comparison of health and behavior outcomes with gonadectomized and sexually intact dogs
Urinary Incontinence After Spaying
One well-known side effect of ovariectomy in female dogs is urinary incontinence, sometimes called urethral sphincter mechanism incompetence. This has historically been attributed to loss of estrogen, but the picture is more complex. The pathophysiology involves changes in tissue structure, collagen content, vascularity, and estrogen receptor density, as well as shifts in FSH and luteinizing hormone levels.30Journal of Veterinary Internal Medicine. Urethral Sphincter Mechanism Incompetence in 163 Neutered Female Dogs: Diagnosis, Treatment, and Relationship of Weight and Age at Neuter to Development of Disease In humans, the parallel question of whether ovariectomy worsens pelvic organ prolapse has been examined too. Data from the Women’s Health Initiative found that bilateral oophorectomy at the time of hysterectomy was not associated with increased risk of cystocele or rectocele, and may even have a slight protective effect when no subsequent hormone therapy was used.31Menopause. Effects of bilateral salpingo-oophorectomy at the time of hysterectomy on pelvic organ prolapse: results from the Women’s Health Initiative trial
Ovariectomy as a Research Tool
Beyond the clinic and the veterinary hospital, ovariectomy is one of the most widely used procedures in biomedical research. Ovariectomized rodents serve as the standard animal model for studying human menopause. These animals develop insulin resistance and accumulate visceral fat, mirroring two hallmarks of metabolic syndrome in postmenopausal women.32PubMed. Ovariectomized rodents as a menopausal metabolic syndrome model. A minireview The model is also used to study osteoporosis, cardiovascular disease, and the efficacy of hormone therapies, because the hormonal profile after ovariectomy in a rat reasonably parallels what happens in a human after surgical menopause.
This animal model has also been instrumental in developing new treatments for menopausal symptoms. Ovariectomized rats exhibit increased skin temperature, hormonal surges, and hypothalamic changes that resemble human hot flashes. Researchers have used this model to test non-hormonal drugs like fezolinetant, a neurokinin 3 receptor antagonist, which was shown to reduce hot-flash-like symptoms in ovariectomized rats without affecting estrogen levels.33European Journal of Pharmacology. Effects of neurokinin 3 receptor antagonist fezolinetant on hot flash-like symptoms in ovariectomized rats Fezolinetant has since been approved for human use, a concrete example of how the ovariectomy model translates into drugs that reach patients.