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Fertility medications

 


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Gonadotropins

The gonadotropins are the pituitary hormones LH and FSH. These hormones work together to promote growth and development of eggs (oocytes) and follicles (cysts containing eggs).

In the natural cycle, FSH is very tightly controlled so that women ovulate only one egg a month. During most of a woman's reproductive life, at any time, there are a number of oocytes that have been released from a protected state (we are unsure how this occurs) and if they receive appropriate stimulation (especially FSH), then they will continue to develop and eventually ovulate. All ovulation inductions play off this idea.

The more advanced approaches use gonadotropins, i.e., medications that contain FSH. There are a number of medications containing FSH that are commonly available These include Follistim, Gonal F, Braville, Menopur, and Repronex. These drugs differ in terms of how they were created, how much LH they contain, and in their general purity (in terms of containing non-bioactive proteins). Recently there have been a number of innovations in the packaging of these medications which makes them easier for some patients to take and may also enable the physician to use them in smaller quantities (e.g., 25 Unit increments as opposed to 75 Unit increments).

Braville, Menopur, and Repronex are all derived by purifying large quantities of urine from post-menopausal women. They are purer versions of the FSH containing drug, Pergonal, which preceded them. They differ from each other by the amount of LH (activity) they contain (1 Unit to 75 Units) which may or may not be desirable depending on the situation. They also contain varying amounts of non-bioactive urinary proteins.

Follistim and Gonal F are members of a second generation of gonadotropins. They are created in the laboratory/factory using recombinant techniques. They also contain some packaging additives, but generally are more pure and more consistent from batch to batch than urinary gonadotropins.

All of these drugs contain FSH, but it is not exactly the same FSH. Structurally, all FSH has the same protein backbone, which defines it to be FSH, but it is modified as the body adds carbohydrate side-chains to it. This leads to slightly different bioactivities between the recombinant and urinary FSHs and between the two brands of recombinant FSHs. In terms of the way that we use these drugs, we do not find this differences to be very important. There are much stronger differences between patients than between drugs and doses need to be varied over time to compensate for those individual and cycle-to-cycle differences.