The medications that help stimulate the ovary to develop mature eggs for ovulation come in two forms: pills taken by mouth and injections. The most commonly prescribed pill to stimulate ovulation (generally of one mature egg) is clomiphene citrate. This pill generally is taken from menstrual cycle days 3 – 7.
It works in the following way:
Clomiphene is an anti-estrogen. It binds in a part of the brain called the hypothalamus, which is essential in stimulating the ovary to grow and release an egg. When clomiphene binds to estrogen receptors in the hypothalamus, it leads to an increased release of an important signaling hormone called GnRH (gonadotropin-releasing hormone). This hormone then binds to another area of the brain called the pituitary gland and leads to the release of FSH (follicle-stimulating hormone), a hormone that directly binds to cells in the ovary, leading to egg growth and maturation.
The most commonly prescribed injections that stimulate the ovary are called gonadotropins. The gonadotropins in these formulations are FSH, and in some cases, a combination of FSH and LH (luteinizing hormone). These injections are taken nightly, typically for 5 – 10 days, and act directly on the cells of the ovary to stimulate egg development. Once a follicle containing an egg reaches a mature size, another hormone injection called HCG is often given to mimic the natural LH surge that occurs at the time of ovulation. This leads to the final maturation and release of the egg.
When the follicular size reaches the target size, we program the egg retrieval process.