Oophorectomy
Oophorectomy (or ovariectomy) is the surgical removal of an ovary or ovaries. In the case of animals, it is also called spaying and is a form of sterilization. Removal of the ovaries in women is the biological equivalent of castration in males, and the term is occasionally used in the medical literature instead of oophorectomy.
In the case of humans, oophorectomies are most often performed due to diseases such as ovarian cysts or cancer; prophylactially to reduce the chances of developing ovarian cancer or breast cancer; or in conjunction with removal of the uterus.
The removal of an ovary together with a Fallopian tube is called salpingo-oophorectomy or bilateral salpingo-oophorectomy if both ovaries and tubes are removed. Oophorectomy and salpingo-oophorectomy are not common forms of birth control in humans; more usual is tubal ligation, in which the Fallopian tubes are blocked but the ovaries remain intact. In many cases, surgical removal of the ovaries is performed concurrent with a hysterectomy. The surgery is then called "ovariohysterectomy" casually or "total abdominal hysterectomy with bilateral salpingo-oophorectomy" (sometimes abbreviated TAH-BSO), the more correct medical term. However, the term "hysterectomy" is often used colloquially yet incorrectly to refer to removal of any parts of the female reproductive system, including just the ovaries.

# Hormone replacement
In general, hormone replacement therapy is somewhat controversial due to the known carcinogenic and coagulative properties of estrogen; however, many physicians and patients feel the benefits outweigh the risks in women who may face serious health and quality of life issues as a consequence of early surgical menopause. The ovarian hormones of estrogen, progesterone, and testosterone are involved in the regulation of hundreds of bodily functions; it is believed by some doctors that hormone therapy programs mitigate surgical menopause side effects such as increased risk of cardiovascular disease , and female sexual dysfunction . There are many options for hormone replacement currently available and a considerable controversy exists in regards to synthetic versus natural or bio-identical regimens.

# Benefits

## Reduced breast cancer risk
Women with a risk of breast cancer, especially those women with mutated BRCA1 and/or BRCA2 genes, have been shown to have a significantly reduced risk of developing breast cancer after prophylactic oophorectomy.  In addition, removal of the uterus in conjunction with prophylactic oophorectomy allows estrogen-based HRT to be prescribed to aid the woman through her transition into surgical menopause, instead of mixed hormone HRT, which has a significant contribution to breast cancer as well.

## Reduced ovarian cancer risk
Women with a risk of ovarian cancer, especially those women with mutated BRCA1 and/or BRCA2 genes, have been shown to have a significantly reduced risk of developing ovarian cancer after prophylactic oophorectomy. Risk is not reduced to zero, however, because the possibility of developing primary peritoneal cancer, which is basically ovarian cancer that begins outside the ovaries, does persist.

## Reduced problems of endometriosis
In rare cases, oophorectomy can be used to treat endometriosis.  This is done to remove a source of hormones that fuel uterine lining growth, thus reducing the overgrowth responsible for endometriosis.  Oophorectomy for endometriosis is usually a last-resort surgery, since hormonal agonists such as Lupron are usually prescribed first to alter the hormonal cycle. Oophorectomy for endometriosis is often done in conjunction with a hysterectomy as a final shot at removing all traces of endometriosis in cases where non-surgical treatments such as hormonal agonists have failed to stop the uterine overgrowth.
Ovarian cyst removal not involving total oophorectomy is often used to treat milder cases of endometriosis when non-surgical hormonal treatments fail to stop cyst formation.  Removal of ovarian cysts through partial oophorectomy is also used to treat extreme pelvic pain from chronic hormonal-related pelvic issues.

# Risks

## Longevity Risk
Removal of ovaries causes hormonal changes and symptoms similar to, but generally more severe than, menopause. Women who have had an oophorectomy are usually encouraged to take hormone replacement drugs to prevent other conditions often associated with menopause. Women younger than 45 who have had their ovaries removed face a mortality risk 1.7 times greater than women who have retained their ovaries. .  Retaining the ovaries when a hysterectomy is performed is associated with greater longevity.  However, hormone therapy is commonly believed by many doctors to mitigate the mortality risks of oophorectomy .
Women who have had bilateral oophorectomy surgeries lose most of their ability to produce the hormones estrogen and progesterone, and lose about half of their ability to produce testosterone, and subsequently enter what is known as "surgical menopause" (as opposed to normal menopause, which occurs naturally in women as part of the aging process). "Surgical menopause" differs from naturally occurring menopause in several respects: Surgical menopause is an iatrogenic procedure, while menopause is a natural event. A menopausal woman has intact functional female organs, a woman with surgical menopause does not. In natural menopause the ovaries generally continue to produce low levels of hormones, while in surgical menopause the ovaries and their hormones are absent, which can explain why surgical menopause is generally accompanied by a more sudden and severe onset of symptoms than natural menopause, symptoms which may continue until natural age of menopause arrives .  These symptoms are commonly addressed through hormone therapy, utilizing various forms of estrogen, testosterone, progesterone or a combination of them.

## Cardiovascular Risk
When the ovaries are removed a woman is at a seven times greater risk of cardiovascular disease,   but the mechanisms are not precisely known. The hormones produced by the ovaries cannot be truly replaced. The ovaries produce hormones a woman needs throughout her entire life, in the quantity they are needed, at the time they are needed, and released directly into the blood stream in a continuous fashion, in response to and as part of the complex endocrine system.

## Bone Density Risk
In women under the age of 50 who have undergone oophorectomy, hormone supplements (usually estrogen) are often prescribed as part of hormone replacement therapy (HRT) to offset the negative effects of sudden hormonal loss (most notably an increased risk for early-onset osteoporosis) as well as menopausal problems like hot flashes that are usually more severe than those experienced by women undergoing natural menopause.
Some studies have found that increased bone loss or fracture risk is associated with oophorectomy. 
Reduced levels of testosterone in women is predictive of height loss, which may occur as a result of reduced bone density,

## Sexuality Risk
Oophorectomy generally greatly impacts sexuality in women, reducing or eliminating the ability to have an orgasm, and lowering sexual desire. This reduction is greater than that seen in women undergoing natural menopause . Some of these problems can be addressed by taking hormone replacement.
Increased testosterone levels in women are associated with a greater sense of sexual desire, and oophorectomy greatly reduces testosterone levels.   Reduction in sexual wellbeing was reported in women who had been given a hysterectomy with both ovaries removed.

# Statistics
According to the Center for Disease Control, 454,000 women in the United States underwent this type of operation in 2004.

# Technique
When performed alone (without hysterectomy), an oophorectomy is generally performed by abdominal laparotomy.

# Managing side effects of prophylactic oophorectomy

### Non-hormonal treatments
The side effects of oophorectomy may be alleviated by medicines other than hormonal replacement. Non-hormonal biphosphonates (such as Fosamax and Actonel) increase bone strength and are available as once-a-week pills.  Low-dose Selective Serotonin Reuptake Inhibitors (e.g. Paxil, Prozac) alleviate vasomotor menopausal symptoms, i.e. "hot flashes".

### Hormonal treatments
Short-term hormone replacement with estrogen, in high-risk BRCA mutation carriers, was not shown to increase the risk of breast cancer in women who are post-oophorectomy. The results were published in JCO in 2004, and the conclusions based on a computerized simulation using models of risk and benefit, a lower level of data than a randomized trial per se. This result can probably be generalized to other women at high risk, in whom short term (i.e., one or two year) treatment with estrogen for hot flashes, may be acceptable.