Ovulation induction is the stimulation of ovulation

Ovulation

Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...

 by medication. It is usually used in the sense of stimulation of the development of ovarian follicles to reverse anovulation

Anovulation

An anovulatory cycle is a menstrual cycle during which the ovaries do not release an oocyte. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause...

 or oligoovulation, but can also be used in the sense of triggering oocyte release from relatively mature ovarian follicles. In any case, ovarian stimulation (in the sense of stimulating the development of oocytes) is often used in conjunction with ("strict") ovulation induction. Also, a few definitions also include ovarian hyperstimulation (stimulating the development of multiple follicles of the ovaries in one single cycle) in the definition of ovarian stimulation. Otherwise, ovarian hyperstimulation may still be a side effect of ovulation induction.

Reversing anovulation or oligoovulation

Ovulation induction in the sense of reversing anovulation or oligoovulation is indicated for women who do not ovulate on their own regularly, such as those with Polycystic ovary syndrome

Polycystic ovary syndrome

Polycystic ovary syndrome is one of the most common female endocrine disorders. PCOS is a complex, heterogeneous disorder of uncertain aetiology, but there is strong evidence that it can to a large degree be classified as a genetic disease....

 (PCOS). The medication which is most commonly used to treat anovulation is clomifene citrate (or clomid), which is a selective estrogen receptor modulator

Selective estrogen receptor modulator

Selective Estrogen Receptor Modulators are a class of compounds that act on the estrogen receptor. A characteristic that distinguishes these substances from pure receptor agonists and antagonists is that their action is different in various tissues, thereby granting the possibility to selectively...

 (SERM) that increases production of gonadotropins by inhibiting negative feedback

Negative feedback

Negative feedback occurs when the output of a system acts to oppose changes to the input of the system, with the result that the changes are attenuated. If the overall feedback of the system is negative, then the system will tend to be stable.- Overview :...

 from estrogen on the hypothalamus.

Also, where anovulation or oligovulation is secondary to another disease, the treatment for the underlying disease can be regarded as ovulation induction, by indirectly resulting in ovulation.

Triggering oocyte release

Ovulation induction in the sense of triggering the release of oocytes from already relatively developed follicles can be more more specifically termed oocyte release triggering. Colloquially, this is known as the "trigger shot." However, the process generally includes acceleration of the final maturation of oocytes as well, and thereby partly overlaps with the processes of ovarian hyperstimulation and reversal of anovulation or oligovulation. The triggering of oocyte release is equivalent to the physiological role the LH surge by luteinizing hormone

Luteinizing hormone

Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell...

.

Administration of medication for triggering of oocyte release avails for sexual intercourse

Sexual intercourse

Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...

 or intrauterine insemination to be scheduled at ovulation, the most likely time to achieve pregnancy. In in vitro fertilization, it avails for final maturation of the oocytes and proper timing of egg retrieval.

Medications that can trigger oocyte release include:

• A low dose of human chorionic gonadotropin
  Human chorionic gonadotropin
  Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
  
   (HCG or hCG), which may be injected after completed ovarian stimulation. Ovulation will occur between 38 and 40 hours after a single HCG injection. It is also used in in vitro fertilization, where it makes the follicles perform their final maturation. A transvaginal oocyte retrieval
  Transvaginal oocyte retrieval
  Transvaginal oocyte retrieval , also referred to as oocyte retrieval or even simply egg collection, is a technique used in in vitro fertilization in order to remove oocytes from the ovary of the female, enabling fertilization outside the body...
  
   is then performed at a time usually between 34 and 36 hours after hCG injection, that is, just prior to when the follicles would rupture. This avails for scheduling the egg retrieval procedure at a time where the eggs are fully mature. HCG injection confers a risk of ovarian hyperstimulation syndrome
  Ovarian hyperstimulation syndrome
  Ovarian hyperstimulation syndrome is a complication from some forms of fertility medication. Most cases are mild, but a small proportion are severe.-Causative medications:...
  
  .
• Oocyte release triggering with a GnRH agonist is a valid alternative to HCG triggering, resulting in an elimination of the risk of ovarian hyperstimulation syndrome
  Ovarian hyperstimulation syndrome
  Ovarian hyperstimulation syndrome is a complication from some forms of fertility medication. Most cases are mild, but a small proportion are severe.-Causative medications:...
  
  . The delivery rate is approximately 6% less than with hCG triggering.

Alternatives

In vitro maturation

In vitro maturation

In vitro maturation is the technique of letting ovarian follicles mature in vitro.-Techniques available:The ability of in IVM depends on how mature the follicle already is...

 is letting ovarian follicle

Ovarian follicle

Ovarian follicles are the basic units of female reproductive biology, each of which is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte . These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single...

s mature in vitro

In vitro

In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

, and this technique can potentially be an alternative both to anovulation reversal and oocyte release triggering. Rather, oocytes can mature outside the body, such as prior to IVF. Hence, no (or at least a lower dose of) gonadotropins have to be injected in the body. However, there still isn't enough evidence to prove the effectiveness and security of the technique.