No ovulation, or anovulation, is a condition where an egg is not released during a woman's monthly cycle. Normally, an egg is produced every month from reproductive organs known as ovaries. The egg is generally released around two weeks before the start of the woman's next menstrual period. If ovulation does not occur, there are many possible causes. Some common examples include being over or underweight, taking excessive exercise, a condition known as polycystic ovary syndrome, diseases of the thyroid gland and stress.
Normal ovulation relies on a complex system of hormones produced by the hypothalamus and pituitary in the brain, and the ovaries in the pelvis. If the system is disrupted at any level, ovulation problems can occur. Ovulation begins with the hypothalamus producing hormones which stimulate another part of the brain known as the pituitary. Pituitary hormones are then released which cause the ovaries to produce estrogen. Feedback between the different hormones serves to regulate the whole system.
The function of the hypothalamus can affected by factors such as stress, not eating enough, or exercising too much. Where there is no ovulation, a problem with the hypothalamus is found to be the cause in around a fifth of cases. Disorders of the pituitary gland, such as tumors which produce a hormone called prolactin, can also prevent ovulation.
In the condition known as polycystic ovary syndrome, or PCOS, eggs fail to mature normally and little or no ovulation takes place. PCOS is found in up to three quarters of women with ovulation disorders. Symptoms of the condition include irregular menstrual periods, excessive body hair, acne and being overweight.
An underactive thyroid is probably the most common hormonal cause of no ovulation. The disease, known as hypothyroidism, affects the levels of reproductive hormones, including estrogen. Symptoms of increased menstrual bleeding and irregular periods may occur. Sometimes hyperthyroidism, or an overactive thyroid, may also result in abnormal menstrual cycles with no ovulation pattern.
In women who have premature ovarian failure, a condition where ovulation does not occur, menopause begins earlier than usual, typically before 40 years of age. Although this condition can not be reversed, many other disorders preventing ovulation can be treated. Women can be helped to achieve a normal weight through changes to diet and exercise, and drugs can be used to regulate abnormal hormone levels.
For hypothalamus problems, a synthetic version of a natural hormone called hCG can be administered using a syringe pump. The pump delivers pulses of hCG and ovulation rates typically improve enough for couples to have a normal chance of conceiving a child. Ovulation induction is a treatment sometimes used for women with PCOS. A drug is given which stimulates the pituitary gland to produce more hormones, increasing the chances of ovulation occurring.