Ovulation is the monthly process that occurs when an egg is released from the ovary. If this process is disordered—whether nonexistent or irregular—achieving pregnancy can be difficult. There are numerous causes of ovulatory irregularities, including hormone and lifestyle reasons.
Polycystic Ovarian Syndrome (PCOS) is a common cause of ovulatory disorders and is discussed in further detail here. PCOS patients usually have abnormally high levels of insulin, which leads to the overproduction of male hormones (androgens) and irregular ovulation.
Advancing age, or reduced ovarian reserve, is another common cause. As eggs “age,” they lose their capacity to develop and fertilize, which results in low estrogen levels and anovulation (lack of ovulation). Menopause occurs when there are few viable eggs left within the ovary; these women must use egg donors to conceive. Menopause can occur very early in some women.
Hyperprolactinemia is a condition characterized by abnormally elevated levels of the hormone prolactin, which is responsible for breast milk production in pregnant women. Abnormally elevated levels in non-pregnant women lead to irregular or absent ovulation. Hyperprolactinemia is usually caused by a small, benign tumor on the pituitary gland that can often be surgically removed. The drug Parlodel (bromocriptine) is effective in reducing prolactin levels.
Excessive exercise and reduced body fat can adversely affect ovulation by causing elevated androgen levels and low estrogen levels. Obesity or elevated body fat can also lead to anovulation by increasing insulin levels, which results in elevated androgen levels. Difficulty with ovulation may occur because androgens are converted to estrogens in body fat. With more fat present, more estrogen is produced, which can prevent normal ovulation.
Treatments for ovulatory disorders seek to correct the underlying cause and/or stimulate ovulation. For example, the drug metformin is used to treat PCOS by reducing insulin levels. Once insulin levels are normalized, androgen levels decrease, and ovulation can occur. The drug Clomid induces ovulation by competing with estrogen binding sites on the hypothalamus, which signals the release of follicle stimulating hormone to directly stimulate the ovaries.