FSH is the hormone produced by the pituitary that is responsible for follicular recruitment and development. FSH exerts its effects directly on the ovaries. In a normal, “non stimulated” cycle, the hypothalamus signals the pituitary to decrease FSH production as estrogen levels rise. In a stimulated cycle (ovulation induction for IUI, IVF, or donor egg),
FSH is given by injection and “overrides” hypothalamic regulation. FSH dosages are adjusted by the infertility specialist to provide optimal egg recruitment and development. Ovulation induction cycles should always be conducted by a reproductive endocrinologist/infertility specialist. Specialists monitor hundreds of IUI and IVF ovulation induction cycles during their Fellowship training.
The first “natural” FSH gonadotropin product was Pergonal which is derived from the urine of post-menopausal women. Along with FSH, it contains contaminants including luteinizing hormone (LH), which some specialists believe improves the “quality” of the ovarian stimulation.
The newer FSH products, including Gonal-F and Follistim, are pure manufactured using genetic recombinant technologies and mammalian cell lines. These products are genetically engineered to be identical to the bodies FSH. Many embryologists believe that pure FSH products produce “higher quality” eggs.
In ovulation induction cycles, it is vital to follow follicular development and adjust dosages precisely according to each patient’s response. Patients are monitored by three processes which include transvaginal ultrasound to confirm the size and number of follicles, estradiol measurements to insure the eggs are healthy, and physical examination. High order multiple births (>=3) can result when too many eggs are ovulated in an IUI cycle. In some cases, the risk is too high and the infertility specialist will cancel the cycle. Also, FSH can produce side effects especially in certain patient types such as the PCOS patient.
One potential adverse event is ovarian hyperstimulation syndrome which can be serious and require hospitalization. Infertility specialists have extensive clinical experience managing these difficult patient types.
High order multiple births from an IVF cycle are less frequent than IUI because the infertility specialist controls the number of embryos transferred to the uterus. Once the eggs are judged “mature”, the patient is given an injection of hCG to finally prepare the eggs for retrieval, usually 36 hours later. There is no effective way to precisely manage how many eggs will be ovulated in an IUI cycle.
Normally, the hypothalamus signals the pituitary to release a surge of LH once the eggs mature to start the ovulatory process. The pituitary cannot produce LH while the patient is taking either Lupron, Ganirelix, or Cetrotide to control their cycle. These drugs prevent premature ovulation that could cause the eggs to release before they can be retrieved thus “loosing” the cycle. The body responds to hCG in the same manner as LH. Therefore, an injection of hCG will initiate ovulation. Genetically engineered LH is also available as Luveris. Once hCG or LH is injected, the egg retrieval is scheduled approximately 36 hours later.