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Follicle Stimulating Hormone

Follicle Stimulating Hormone (FSH) containing drugs are used to stimulate a follicle (egg) to develop and mature They are also used to stimulate the development of multiple eggs for in vitro fertilization (IVF).

Serono Laboratories first introduced FSH containing products in the United States under the trade name Pergonal. These first products were "natural" in that they were derived and purified from the urine of postmenopausal women. Because they were human derived, they also contained impurities, notably luteinizing hormone (LH). They also had to be administered by intramuscular injection, which is painful and inconvenient.

More recent products include Gonal-F, and Follistim, which are produced using genetic recombinant technology. These FSH products are pure and can be given subcutaneously (just beneath the skin). Bravelle and Menopur are highly purified "human derived" products that can also be given subcutaneously. Serono recently released Luveris (recombinant LH) for use in patients that are hypogonadotropic (have very low levels of gonadotropins).

How FSH works

FSH is produced by the pituitary gland under the influence of Gonadotropin-releasing hormone (GnRH), also known as Luteinizing-hormone releasing hormone (LHRH), which is released by the hypothalamus. In a normal cycle, levels of FSH vary in relationship to hormones such as estrogen. 

When FSH is given by injection, it directly stimulates the recruitment and development of follicles in contrast to Clomid, which works at the hypothalamus. Numerous eggs are needed in IVF cycles as some are immature and cannot be fertilized. As patients undergo ovulation induction with FSH, they are carefully monitored by estradiol measurements, ultrasound to visualize the ovaries and follicles, and physical examination. 

There is debate among physicians and embryologists as to the need for LH in FSH stimulated cycles. All physicians administer these products using individualized protocols for each patient. Many physicians believe that a minute quantity of LH causes a "better stimulation" in some patient groups. Mixed protocols using Follistim (FSH) and Bravelle, Menopur or Repronex are often used.

Possible FSH Side Effects

FSH should only be administered by an fertility specialist / Reproductive Endocrinologist thoroughly trained in its use. Patients must be monitored and dosages adjusted to avoid potentially serious side effects such as ovarian hyperstimulation. Most high order multiple births (triplets, or more) reported by the media are due to FSH stimulated intrauterine insemination (IUI) cycles that were not managed by a fertility specialist.

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