Ovulation is controlled by a series of hormonal events occurring each month during the ovulation cycle. During the first part of the ovulation cycle, the hypothalamus releases “gonadotropin releasing hormone” or GnRH which causes the production of follicle stimulating hormone (FSH) and luteinizing hormone (LH) by the pituitary. FSH is responsible for follicular growth and the development of the eggs during the ovulation cycle. LH supports the theca cells in the ovaries that provide androgens and hormonal precursors for the production of estrogen.
Successful ovulation requires that he hypothalamus monitor levels of FSH, LH, and estrogen. The hypothalamus performs its reproductive functions by signaling the pituitary gland to increase or decrease production of these hormones. For example, the hypothalamus registers increasing estrogen levels during early egg development. As healthy follicles develop, they produce increasing amounts of estrogen, which signals a decline in FSH production. Ovulation requires precise control of these reproductive hormones by the hypothalamus.
Once the eggs mature and are ready for ovulation, the hypothalamus signals the pituitary to release a surge of LH, which finally prepares the eggs and causes ovulation 36-38 hours later. Ovulation induction patients receive an injection of hCG, which mimics the LH surge. This is necessary because these patients receive fertility drugs that block spontaneous ovulation.
The follicular structure remaining after ovulation is termed the “corpus luteum”. It produces progesterone which is needed for proper endometrial support and development. The endometrium (uterine lining) must thicken and become more vascular to support the developing embryo. The pre-embryo implants into the endometrium and grows with subsequent fetal development and formation of the placenta. The placenta then produces progesterone which supports the pregnancy.
Ovulatory disorders can be caused by conditions such as polycystic ovarian syndrome (PCOS). In PCOS patients, the androgen levels (male hormones) are too high and thus interfere with the ovulatory cycle. Increased androgens are due to abnormally high insulin levels (hyperinsulenemia), and PCOS can sometimes be treated by lowering insulin levels with drugs like Metformin (glucophage). Once the androgen excess is corrected, spontaneous ovulation will often resume. Some patients lose weight with Metformin, which also helps with ovulation.
Ovulation disorders can be caused by elevated prolactin levels (hyperprolactenemia). Prolactin is the hormone responsible for breast milk production, and levels normally rise after conception. Elevated prolactin levels in the absence of pregnancy can cause ovulatory irregularities. Elevated prolactin levels are sometimes due to a small nonmalignant tumor on the pituitary, which can be removed surgically or treated with medication such as bromocriptine or cabergoline.
Ovarian Factor Infertility(Add anchor #ovarian)
Ovarian factor occurs when the ovaries do not contain enough quality eggs. Women are born with a lifetime’s supply of eggs and one/two is ovulated each month in the normal menstrual cycle. Unfortunately, as women age so do their eggs and quality declines until the menopause when eggs lose their ability to fertilize.
Sometimes egg quality declines earlier in life, a condition sometimes termed diminished ovarian reserve or ovarian failure. The reason(s) for this decline are unknown but probably have a genetic basis. One of the first signs of diminishing egg quality is an abnormally elevated day 3 FSH hormone level. Estrogen levels don't increase and FSH production continues. Diminished ovarian reserve is followed by ovarian failure.
Ovarian failure means a woman will have to use an egg donor to have a child. Egg donors are young, healthy females who agree to let another woman use her eggs in an IVF cycle. The donor's eggs are combined with the partner’s sperm, meaning the child will have the genetic makeup of the father and the donor.
Donor egg is also a wonderful option for women who were born without ovaries or who lost ovarian function due to disease or cancer chemotherapy and/or radiation or surgery. These women can still produce healthy children using a donor's eggs and a partner's sperm. Please see our donor egg Web pages for more information.
Fortunately, success rates for donor egg IVF cycles are high and women can have healthy children well into their late forties.