Physiology of ovulation for infertility treatments forms the basis of all treatments offered to infertility patients. Infertility is one of the most common disorders among couples. It is the inability of a couple to conceive and reproduce. Infertility is defined as the failure to conceive after one year of regular sexual activities, without any use of contraceptive techniques. Infertility is also directly associated with the inability of a woman to carry a pregnancy to live birth. Around 1 in every 10 couples is affected due to infertility.

Ovulation is the process in which a mature egg, released from a female ovary, is fertilized by the male sperm cells. Normally, only one egg is released at a time, whereas, occasionally, two or more erupt during the menstrual cycle.

The egg erupts from the ovary on the 14th to 16th day of an approximate 28-day menstrual cycle. When it is not fertilized, the egg is passed from the reproductive tract during the menstrual bleeding, which generally starts in about two weeks after ovulation. There are also chances that an egg is not released during a cycle, and such a condition is called an anovulatory cycle.

So, as we know, the physiology of ovulation for infertility treatments is largely administered by the menstrual cycle, which is governed by the hypothalamo pituitary axis. It is this hypothalamo pituitary axis that controls the pituitary as well as the gonadal axis.

During ovulation, several hormones are stimulated and produced in the pituitary gland. Two main hormones released during ovulation are – follicle-stimulating hormone and luteinizing hormone.

It is after the egg leaves the ovary that the walls of the follicle close again, and the space that was previously occupied by the egg, begins to fill with new cells, known as the corpus luteum.

The corpus luteum secretes the female hormone – progesterone that helps to keep the uterine wall receptive to a fertilized egg. When the egg is not fertilized, the corpus luteum stops secreting progesterone in around nine days after a female would have ovulated.
On the other hand, further physiology of ovulation states that when the egg is fertilized, the process of progesterone secretion is undertaken first by the corpus luteum and then by the placenta until the child is born.

Progesterone works in blocking the release of more hormones from the pituitary gland so that further ovulation does not occur once the female is pregnant.

Then there is GnRH (Gonadotropin-releasing hormone) The GnRH is a neurohormone, responsible for the release of follicle-stimulating hormone and luteinizing hormone from the anterior pituitary. The GnRH is a tropic peptide hormone synthesized and released from GnRH neurons within the hypothalamus.

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Dr. Madhuri Patil, IVF specialist, Dr. Patil’s Endoscopy and Fertility Center, Bangalore