What does ovulate mean?
Ovulation is a process where one of the ovaries releases an egg cell (ovum) into the fallopian tube. Ovulate is therefore the action of the ovary in releasing the ovum from the ovary. If a woman is to fall pregnant, she has to ovulate prior to unprotected intercourse. The sperm cells from the male then travel to the egg cell and fertilize it. Pregnancy has then occurred. As simple as this may seem, the process is quite complex. In order to ovulate, there are a host of other factors that need to be carefully coordinated. Ovulation is a single event in the menstrual cycle. It marks the end of the first phase and start of the second phase of the menstrual cycle.
The first phase is the follicular phase and starts on the first day of the last menstrual period. It primarily involves two pituitary hormones and two ovarian hormones. FSH (follicle-stimulating hormone) and LH (luteinizing hormone) are released by the pituitary gland and travel through the bloodstream to act on the ovaries. A follicle within the ovary matures and eventually releases the ovum – ovulation. The follicular phase ends here.
The now “empty” follicle transforms into the corpus luteum and secretes the hormones, estrogen and progesterone. The ovum moves down the fallopian tube and awaits fertilization by a sperm cell while the estrogen and progesterone prepares the inner lining of the uterus (endometrium). If fertilization does occur then the fertilized egg will implant in the newly prepared uterus. Pregnancy has occurred and a woman will not ovulate during the rest of pregnancy and even for a while after childbirth.
If pregnancy does not occur then between 12 to 16 days after ovulation, menstruation will occur. Menstruation is the expulsion of the thickened inner lining of the uterus (endometrium) that was prepared for pregnancy. The onset of the menstrual period marks the end of one menstrual cycle and the start of the next cycle. The estrogen and progesterone levels gradually drop and FSH and LH prepare the ovary for ovulation again.
If ovulation does not occur then the cycle is known as an anovulatory cycle. Anovulation means that ovulation did not occur. It is one of the most common reasons why women do not fall pregnant. For ovulation to occur, the following needs to be present :
- Healthy ovaries with sufficient follicles containing ova (egg cells).
- Follicle stimulating hormone (FSH) from the pituitary gland.
- Gonadotropin-releasing hormone (GnRH) which stimulates the pituitary gland to release FSH.
Although rather simplistic, these three factors are essential for ovulation. Various other factors can impact on ovulation as well but if the ovaries are healthy, pituitary and hypothalamic regulation normal and there is no disturbance of FSH, ovulation should occur.
There are a number of ovarian diseases that can affect ovulation. In these instances the ovaries do not respond as it would to FSH. Follicles may not mature and ova (egg cells) are not released. The main ovarian diseases that can affect ovulation includes :
- Ovarian cancer where a malignant tumor develops in the ovary. The cancer can destroy healthy ovarian tissue and secrete hormones that block ovulation. However, it is important to note that ovarian cancer more often affects a single ovary thereby leaving the other ovary intact.
- Benign ovarian tumors that secrete large amounts of hormones like estrogen which disturbs the negative feedback mechanism necessary for the hypothalamus to stimulate the pituitary gland to secrete FSH.
- Premature ovarian failure is a condition where the follicles are depleted or dysfunctional before a woman reaches 40 years of age. It is also known as hypergonadotropic hypogonadism. Although the condition is sometimes referred to as premature menopause, this term is inaccurate.
- Polycystic ovarian syndrome (PCOS) where cysts form in the ovaries destroying healthy ovarian tissue. It is a condition that primarily has a hormonal association marked by higher than normal androgen levels and often insulin resistance.
- Scarred ovaries may result from surgery or infection. Any inflammatory ovarian condition or damage to the ovary can result in the formation of scar tissue.
- Ovarian injury may lead to inflammation where the ovary starts malfunctioning and the release of the egg cell (ovulation) does not occur. This may occur with surgery, radiation therapy, infections and chemical poisoning. Eventually scar tissue may form.
There are a host of hormone problems that can affect ovulation. Although the main regulating hormones that control ovulation are secreted by the pituitary gland, the gland in turn is regulated and affected by a host of other hormones. Some of the more common hormonal problems that can prevent ovulation includes :
- Polycystic ovarian syndrome is a condition where the levels of follicle stimulating hormone (FSH) is lower than normal despite normal or even increased levels of other sex hormones. Cysts in the ovaries and insulin resistance are commonly seen in these cases.
- Pituitary gland problems affects the secretion of FSH thereby hampering ovulation. The main pituitary problems arises with damage to the pituitary gland during neurosurgery or radiation exposure, tumors like pituitary adenomas and pituitary apoplexy.
- Hypothalamic disorders affects the release of gonadotropin-releasing hormone (GnRH) which regulates the pituitary gland’s secretion of FSH. The more common causes of hypothalamic disorders that affect ovulation includes tumors, traumatic head injury like during motor vehicle accidents and radiation exposure.
- Thyroid disorders, either hyperthyroidism (overactive thyroid) or hypothyroidism (underactive) thyroid, can affect ovulation as well as menstruation.
- Hyperprolactinemia where the prolactin levels in the blood are higher than normal. This blocks GnRH secretion.
- Hyperinsulinemia where the blood insulin levels are higher than normal usually as a result of insulin resistance.
- Adrenal insufficiency where the adrenal gland is underactive and there are lower than normal amounts of androgens (male sex hormones) released by the adrenals.
- Cushing syndrome is a condition that arises with prolonged exposure to high levels of cortisol, a hormone secreted by the adrenal glands.
There are several other causes that can prevent ovulation. Some of these factors affect the hormone levels, others the ovaries but there are instances where the exact mechanism is not full understood. These causes include :
- Starvation and strict dieting
- Excessive exercise
- Eating disorders
- Severe blood loss
- Major psychological stress
- Severe illness
- Oral contraceptives