Unlike Clomid, FSH (Gonal-F, Repronex, Follistim, Menopur, others) stimulates the ovaries directly causing the recruitment of multiple follicles. Clomid is often administered by the OB/GYN and it should not be used longer than three months. Clomid pregnancies after this period are rare. Because FSH has a direct stimulatory effect on the ovaries, FSH should only be used by reproductive endocrinologists, fertility specialists thoroughly trained in its administration. This is especially true for women who may be suffering from PCOS and who can have exaggerated responses to FSH.
There are two “classes” of FSH products: Menopur, Bravelle, and Humegon- these products are “human derived” being extracted from the urine of postmenopausal women who have high levels of FSH. These products contain LH and other impurities. Fortunately, they can now be administered subcutaneously instead of intramuscularly.
The second “class” includes the man made gonadotropins created by using mammalian cell cultures and genetic recombinant technology. These FSH products are identical to the bodies, have no impurities, and can also be given subcutaneously.
There is some debate as to which class of gonadotropin provides the best stimulation. Some embryologists and physicians believe that pure FSH may result in higher quality embryos and others believe the LH in the natural products produces a “better” stimulation. Dosages of all of these products are individualized for each specific patient taking into account the cause(s) of her infertility and previous treatment history.
Because these drugs stimulate the ovaries directly they can cause the development of many, sometimes more the 20, eggs within the ovarian follicles. This is critical for in vitro fertilization (IVF) where numerous eggs are needed for retrieval culture and embryo development. However, the stimulation must be carefully monitored via ultrasound to measure and count the follicles and estradiol hormone levels must be assessed. The reproductive endocrinologist infertility specialist carefully monitors follicular development and adjusts dosages accordingly to avoid potential serious side effects such as ovarian hyperstimulation syndrome. This control is made possible by drugs such as Lupron and Antagon (discussed separately)
Using IVF, a known number of embryos are transferred to the uterus thus helping to control the possibility of high order multiple births. This is not the case with intrauterine insemination (IUI) where the precise number of eggs ovulated cannot be exactly controlled.
Most high order multiple births (>3) reported by the media are a result of FSH stimulated IUI cycles that were often administered by physicians who are not subspecialty trained in reproductive endocrinology and infertility.
Great care must be taken to insure that that the stimulation cycle produces an appropriate number of eggs thus reducing the chance of multiples. Sometimes the IUI cycle will have to be cancelled because of an unacceptable risk of high order multiple births or it may be converted to an IVF cycle.