Editing Anovulation (section)

==Causes==

Hormonal imbalance is the most common cause of anovulation and is thought to account for about 70% of all cases. About half the women with hormonal imbalances do not produce enough follicles to ensure the development of an [[ovule]], possibly due to poor hormonal secretions from the [[pituitary gland]] or the [[hypothalamus]]. The pituitary gland controls most other hormonal glands in the human body. Therefore, any pituitary malfunctioning affects other glands under its influence, including the [[ovaries]]. This occurs in around 10% of cases. The pituitary gland is controlled by the hypothalamus. In 10% of cases, alterations in the chemical signals from the hypothalamus can easily seriously affect the ovaries. There are other hormonal anomalies with no direct link to the ones mentioned above that can affect [[ovulation]]. For instance, women with [[hyperthyroidism|hyper-]] or [[hypothyroidism]] sometimes have ovulation problems. [[Thyroid]] dysfunction can halt ovulation by upsetting the balance of the body's natural reproductive hormones.

Currently, the four main causes of ovulatory disorders are polycystic ovarian syndrome (PCOS), [[hypogonadotropic hypogonadism]] (HA), primary ovarian insufficiency (POI), and [[hyperprolactinemia]].<ref name=":0" />

=== Polycystic ovarian syndrome ===
Women with PCOS make up the greatest portion of anovulatory women in clinical practice. The criteria for a PCOS diagnosis is referred to as the Rotterdam criteria and consists of

# [[oligoovulation]] and/or anovulation
# excess androgen activity
# polycystic ovaries (by [[gynecologic ultrasound]])<ref name=":1" />

=== Hypogonadotropic hypogonadism ===
Hypothalamic causes of HA include functional hypothalamic amenorrhea (FHA) and isolated gonadotropin-releasing hormone (GnRH) deficiency.<ref name="FARIDDiamanti-Kandarakis2009" /> Laboratory findings of low serum estradiol and low FSH are associated with the decrease in hypothalamic secretion of GnRH.<ref name="FARIDDiamanti-Kandarakis2009" />

A rare form of HA that presents as primary amenorrhea can be due to a congenital deficiency of GnRH knows as idiopathic hypogonadotropic hypogonadism or, Kallmann syndrome if it is associated with anosmia.<ref name="FARIDDiamanti-Kandarakis2009" /> Infiltrative disease or tumors affecting the hypothalamus and pituitary can result in HA.<ref name="FARIDDiamanti-Kandarakis2009" />

FHA accounts for around 10–15% of all cases of anovulation. Weight loss or [[Anorexia nervosa|anorexia]] can lead to FHA by causing a hormonal imbalance, leading to irregular ovulation (dysovulation). It is possible that this mechanism evolved to protect the mother's health. A pregnancy where the mother is weak could pose a risk to the baby's and mother's health. On the other hand, excess weight can also create ovarian dysfunctions. Dr Barbieri of Harvard Medical School has indicated that cases of anovulation are quite frequent in women with a BMI ([[body mass index]]) over 27&nbsp;kg/m2.

=== Primary ovarian insufficiency ===
POI was previously referred to as premature ovarian failure (POF) and diagnosed when menopause occurred before age 40 but occurs in only 1 percent of all women.<ref name="ChavarroRich-Edwards2007">{{cite journal|last1=Chavarro|first1=Jorge E.|last2=Rich-Edwards|first2=Janet W.|last3=Rosner|first3=Bernard A.|last4=Willett|first4=Walter C.|year=2007|title=Diet and Lifestyle in the Prevention of Ovulatory Disorder Infertility|journal=Obstetrics & Gynecology|volume=110|issue=5|pages=1050–1058|doi=10.1097/01.AOG.0000287293.25465.e1|issn=0029-7844|pmid=17978119|s2cid=6719868}}</ref> The [[ovaries]] can stop working in about 5% of cases. This may be because the ovaries do not contain eggs. However, a complete blockage of the ovaries is rarely a cause of [[infertility]]. Blocked ovaries can start functioning again without a clear medical explanation. In some cases, the egg may have matured properly, but the [[Ovarian follicle|follicle]] may have failed to burst (or the follicle may have burst without releasing the egg). This is called [[Luteinised unruptured follicle syndrome|luteinized unruptured follicle syndrome]] (LUFS). Physical damage to the ovaries, or ovaries with multiple cysts, may affect their ability to function. This is called ovarian dystrophy.

=== Hyperprolactinemia ===
Hyperprolactinemia anovulation makes up 5 to 10 percent of women with anovulation. Hyperprolactinemia inhibits gonadotropin secretion by inhibiting GnRH.<ref name=":2">{{Citation |last=Rebar |first=Robert |title=Evaluation of Amenorrhea, Anovulation, and Abnormal Bleeding |date=2000 |url=http://www.ncbi.nlm.nih.gov/books/NBK279144/ |work=Endotext |editor-last=Feingold |editor-first=Kenneth R. |place=South Dartmouth (MA) |publisher=MDText.com, Inc. |pmid=25905367 |access-date=2022-11-14 |editor2-last=Anawalt |editor2-first=Bradley |editor3-last=Boyce |editor3-first=Alison |editor4-last=Chrousos |editor4-first=George}}</ref> Hyperprolactinemia can be confirmed by several measurements of serum prolactin.