Can Having One Ovary Removed Cause Hormonal Imbalance?

Removing one ovary, a procedure called unilateral oophorectomy, does not usually cause the kind of dramatic hormonal crash that losing both ovaries would. The remaining ovary has a remarkable ability to pick up the slack, growing larger and maintaining much of the body’s hormone output. That said, measurable hormonal shifts do occur: certain markers of ovarian reserve drop, and menopause tends to arrive roughly one to two years earlier than it otherwise would. Whether those shifts amount to a “hormonal imbalance” you would actually feel depends on your age at surgery, your baseline ovarian reserve, and how your body responds to the compensation process.

Why the Remaining Ovary Grows

When one ovary is removed, the other one does not simply carry on at its original capacity. It physically enlarges in a process called compensatory hypertrophy. A study examining ovarian volumes in girls and adolescents who had undergone unilateral oophorectomy found that more than 62% of the remaining ovaries were larger than age-matched norms.¹ This enlargement is not a disease process or something to worry about on an ultrasound. It is the body’s way of ramping up the solo ovary’s output to compensate for the missing one.

The mechanism behind this involves a feedback loop between the ovaries and the brain. With one ovary gone, the total amount of hormones reaching the pituitary gland dips slightly. The pituitary responds by sending stronger signals, which stimulate the remaining ovary to grow more follicles and produce more hormones. In many cases, this compensation is effective enough that day-to-day hormone levels stay within a functional range and menstrual cycles continue normally.

Measurable Hormone Shifts After Surgery

Even with compensation, lab work can pick up differences between someone with one ovary and someone with two. Anti-Müllerian hormone, or AMH, is a blood marker that reflects how many egg-containing follicles the ovaries still hold. In women with one ovary, AMH tends to be about half the level seen in women with two ovaries. One study found a median AMH of 1.1 in one-ovary patients compared to 2.2 in two-ovary patients. Follicle-stimulating hormone (FSH), the signal from the brain that tells the ovaries to work harder, was also higher in the one-ovary group, with a median of 7.4 compared to 6.2.²

A lower AMH and higher FSH do not automatically mean you will feel different. AMH is primarily a marker of how many eggs remain, not of how much estrogen or progesterone you produce on a given day. Many women with one ovary continue to have regular periods, ovulate monthly, and show no noticeable symptoms of hormone deficiency. The shifts are more relevant to fertility planning and to predicting when menopause might arrive than to how you feel in your daily life.

The Menopause Timeline Moves Up

The most consistent long-term hormonal consequence of losing one ovary is that menopause arrives earlier. The question is by how much, and the answer depends on the study and the population, but the findings cluster around one to two years.

A large Norwegian survey of over 23,500 women found that those who had undergone unilateral oophorectomy reached menopause at an average age of 49.6, compared to 50.7 for women with both ovaries intact. That one-year gap held up even after adjusting for factors like smoking, body mass index, and number of pregnancies.³ A Japanese cohort of over 24,000 women showed a similar gap, and a Danish cohort of nearly 18,000 women found an even larger shift of about 1.8 years earlier.⁴

One to two years may not sound dramatic, and for most women it is not. But the shift matters more than its size suggests, because it is an average. Some women will barely notice a difference, while others, particularly those who already had a lower-than-average ovarian reserve before surgery, could experience a more pronounced acceleration. And if menopause arriving a year or two early pushes someone across the threshold into early menopause (before age 45), the health implications change significantly.

When Surgery Happens Young, the Effect Is Stronger

Age at the time of surgery turns out to be one of the most important variables. A longitudinal community-based cohort study found that the risk of reaching menopause earlier was strongest when the ovary was removed in early adulthood. For women who had the surgery around age 30, the risk of earlier menopause was more than double compared to those who had it closer to the natural menopause age. By contrast, having the surgery in your late 40s or 50s made little practical difference to the menopause timeline.⁵

That same study found that unilateral oophorectomy was associated with roughly 90% higher odds of early menopause (before age 45) and nearly four times the odds of premature ovarian insufficiency (before age 40).⁵ Those are relative risks, so the absolute numbers are still small for most women. But for someone who has an ovary removed at 25 for a cyst or endometriosis, these findings mean the hormonal consequences could play out over a longer timeline and deserve monitoring.

The Danish cohort data reinforced this pattern: younger age at surgery correlated in a linear fashion with younger age at menopause.⁴ The remaining ovary does compensate, but it was never designed to run solo for decades. The longer it has to do so, the more it draws down its finite pool of follicles, and the sooner that pool runs out.

Why Most People Have the Surgery in the First Place

It helps to know that unilateral oophorectomy is not a procedure performed casually. In a review of over 1,800 women who had one ovary removed before menopause, about 74% of surgeries were for benign conditions, with simple ovarian cysts being the most common finding, accounting for nearly 59% of cases.⁴ Other reasons include ovarian torsion (where the ovary twists on its blood supply, cutting off flow), endometriomas, borderline tumors, and ectopic pregnancies involving the ovary.

The reason for surgery matters because the underlying condition itself can affect hormone levels. A large endometrioma, for example, may have already been destroying healthy ovarian tissue for years before the ovary is removed. In such cases, the hormonal “damage” was done by the disease, and removing the diseased ovary simply reflects the loss that was already underway. Conversely, removing a healthy-looking ovary because of torsion is a cleaner situation where the hormonal impact is more purely surgical. When you hear about hormonal changes after unilateral oophorectomy, keep in mind that the research is capturing a mix of these different stories.

How This Differs From Losing Both Ovaries

The distinction between losing one ovary and losing both is enormous, and it is worth making explicit because people sometimes confuse the two when reading about oophorectomy. Bilateral oophorectomy before menopause causes immediate surgical menopause, with an abrupt loss of estrogen, progesterone, and a significant share of testosterone. Without hormone replacement, most of these women develop severe symptoms of estrogen deficiency and face increased risks of osteoporosis, cardiovascular disease, and cognitive decline.⁶

Unilateral oophorectomy is a fundamentally different situation. You still have a functioning ovary producing hormones in real time. There is no sudden menopause. The ovarian reserve is reduced but not eliminated. The health risks associated with early bilateral oophorectomy, such as accelerated bone loss and cardiovascular problems, are not typically observed after removal of just one ovary. In fact, one large study found that women who had undergone unilateral oophorectomy actually had a slightly lower rate of cardiovascular death compared to women who had not had any ovarian surgery.⁷ That finding likely reflects the fact that keeping even one ovary preserves the protective hormonal environment that bilateral removal destroys.

Bone Density and Cardiovascular Considerations

The relationship between ovarian surgery and bone health mostly concerns bilateral oophorectomy. In high-risk women who had both ovaries removed, one study documented an average bone density loss of about 8.5% in the lumbar spine and roughly 5.7% in the hips over just 18 months without hormone therapy.⁸ Those are striking numbers for such a short window, and they underscore why bilateral oophorectomy before menopause is approached cautiously and usually paired with hormone therapy.

For women with one ovary, the concern is subtler. The remaining ovary continues producing estrogen, which is the primary protector of bone density. As long as that ovary functions, the acute bone loss seen after bilateral removal should not occur. The indirect risk comes later: if menopause arrives one to two years early, that is one to two fewer years of estrogen exposure, and bone loss after menopause proceeds regardless of how many ovaries you had. A woman who reaches menopause at 48 instead of 50 accumulates slightly more years of postmenopausal bone loss by any given age. The effect is real but gradual, and it is something a doctor can monitor with bone density scans in the years around menopause rather than something that requires immediate intervention after surgery.

On the cardiovascular side, the protective finding mentioned earlier, that unilateral oophorectomy was associated with lower cardiovascular mortality rather than higher, is reassuring but somewhat counterintuitive.⁷ One explanation is that women who had only one ovary removed were compared to a general population that included women who would later have bilateral oophorectomy and its associated risks. Another possibility is that the conditions leading to unilateral oophorectomy, like cyst removal, select for otherwise healthy women who are receiving medical care. The evidence is not strong enough to say losing one ovary protects your heart, but it does suggest it is unlikely to harm it.

Fertility After Losing One Ovary

For women still planning to conceive, the hormonal shifts after unilateral oophorectomy raise a practical question: will it be harder to get pregnant? The short answer for most women is that natural conception remains possible. The remaining ovary ovulates, and ovulation from one side can still result in pregnancy from either fallopian tube, since the egg can sometimes migrate. Menstrual cycles typically continue, though some women report a period of irregular cycles in the months immediately following surgery as the remaining ovary adjusts.

The lower AMH and higher FSH discussed earlier do affect the picture for women pursuing assisted reproduction. These markers influence how many eggs can be retrieved in a single IVF cycle, and with one ovary, fewer follicles are available to stimulate. However, research comparing IVF outcomes in one-ovary and two-ovary patients has found that key outcomes like pregnancy rates can be comparable when treatment is adjusted accordingly.² The compensatory hypertrophy of the remaining ovary appears to help here, making it more responsive to fertility medications than a single unstimulated ovary would be.

The more pressing fertility concern is timeline. If menopause is coming one to two years earlier, the window for conception also closes a bit sooner. Fertility declines for several years before menopause actually arrives, so the practical effect may be felt earlier than the menopause date itself. Women who have an ovary removed in their 20s or 30s and want children later should discuss this timeline shift with a reproductive specialist, not because pregnancy is unlikely, but because proactive planning gives better outcomes than discovering the narrower window by surprise.

What Symptoms to Watch For

In the weeks after surgery, some women do notice hormonal symptoms: irregular periods, mood changes, hot flashes, or changes in libido. These usually reflect the body’s transition period while the remaining ovary ramps up production and the pituitary gland recalibrates its signaling. For most women, these symptoms resolve within a few menstrual cycles as compensation takes hold.

If symptoms persist beyond three to six months, or if you stop getting your period entirely, that warrants blood work. Persistent hot flashes, night sweats, vaginal dryness, or mood disturbances after unilateral oophorectomy could signal that the remaining ovary is not compensating adequately. This is more likely if the remaining ovary was already compromised by endometriosis, prior surgery, or another condition, or if you were already approaching perimenopause before the surgery.

Monitoring typically involves checking FSH and estradiol levels. A persistently high FSH with low estradiol would suggest the remaining ovary is struggling. AMH can provide a snapshot of remaining ovarian reserve. These are not tests you need to run repeatedly if you feel fine and your cycles are normal, but they become useful if something seems off. The goal is not to prevent the inevitable decline in ovarian function that happens with age, but to catch an unexpectedly early decline so it can be managed.

Testosterone and Ovarian Androgens

One aspect of ovarian hormones that gets less attention is androgen production. The ovaries produce about half of the body’s testosterone, with the adrenal glands covering the rest. After unilateral oophorectomy, total androgen production may drop somewhat, since you now have half the ovarian tissue generating it. The remaining ovary compensates partially, and the adrenal contribution continues, so a catastrophic drop in testosterone is not expected.

Still, some women notice subtle changes that could relate to lower androgen levels: reduced libido, lower energy, or a vague sense of diminished vitality. These symptoms overlap with many other causes, including the stress of surgery itself, and they are difficult to attribute definitively to androgen changes without testing. Testosterone levels in women are already low compared to men, and the normal range is wide, making it hard to pin down what counts as “too low” for a given individual. If these symptoms are persistent and bothersome, a conversation with an endocrinologist or gynecologist who is comfortable managing androgen levels in women is a reasonable step.

When Hormone Therapy Comes Into Play

For women with one remaining ovary, hormone replacement therapy is not routinely needed. The whole point of keeping one ovary is to preserve natural hormone production, and in most cases that works. Hormone therapy becomes relevant in two scenarios.

The first is if the remaining ovary fails prematurely. If a woman with one ovary enters menopause before 45, the same considerations that apply to any woman with early menopause apply here. Estrogen therapy, often combined with progesterone if the uterus is still present, is recommended until at least the average age of natural menopause to protect bones, the cardiovascular system, and cognitive function.

The second scenario is regular-timing menopause that happens to arrive a bit early because of the prior surgery. In this case, the decision about hormone therapy is the same as for any menopausal woman: based on symptom burden, personal risk factors, and shared decision-making with a provider. The prior unilateral oophorectomy does not change the calculus much. It simply means you might be having the conversation at 49 instead of 51.

The important point is that unilateral oophorectomy does not in itself create the kind of hormone emergency that bilateral oophorectomy does. Women who lose both ovaries before menopause face an immediate and severe hormone deficit that requires replacement unless there is a compelling medical reason not to.⁶ Women who lose one ovary face a long, slow drawdown of ovarian reserve that is shifted modestly forward in time. The difference in urgency is real and should inform how you think about your health trajectory after surgery.