Because different FSH preparations are available, the question of variability in their potency to induce sperm production and paternity arises. Unfortunately, no direct comparison between hMG, highly purified preparations, and recombinant FSH in the treatment of male hypogonadism is available. Analysis of the studies that have been performed using individual preparations in the past is complicated by the fact that different therapeutic regimens were used.
Both hMG and uFSH contain urinary protein contaminants, which are believed to contribute to hypersensitivity reactions and reduce their purity to less than 5%. Through the application of immunochromatography with monoclonal antibodies against FSH, increased purity of more than 95% is achieved in uFSH-HP, but the purest preparation available is recombinant FSH. Furthermore, batch-to-batch consistency and the potential for limitless quantities is advantageous for rhFSH (46). On the other hand, the cost of rhFSH is three times as high as the price of the earlier FSH preparations.
Recently, the potential risks of transmission of prion disease from urinary-derived gonadotropin preparations have been discussed. Because prion disease is believed to be transmitted predominantly by the ingestion of infected nervous tissue, and urine is believed not to be infective according to current advice from the World Health Organization, precautions concerning the application of uFSH are not advised. Furthermore, the urinary preparations have been widely used for 40 yr, and no infections have been described. Because rhFSH is not of human or animal origin, the potential for infections that are transmitted from living organisms is believed to be absent, but because the cell culture medium includes fetal calf serum, it could potentially be infected.
Nevertheless, all of the gonadotropin preparations have a good safety record without evidence of contamination, and there is no need to change current prescribing habits (47). A pharmacokinetic-pharmacodynamic study with rhFSH in patients with hypogo-nadotropic hypogonadism showed dose linear serum FSH levels (48), and the pharmacokinetics of recombinant and urinary FSH are similar (49).
The efficiency of rhFSH compared to uFSH or hMG has been evaluated by different meta-analyses, based on pregnancy rates in in vitro fertilization cycles. Reports are contradictory, with two demonstrating an increase in pregnancy rates in the order of 5% in favor of rhFSH (50,51), whereas the other showed no treatment benefit (52). Although these data refer to ovarian and not to testicular stimulation, taking all information available, there is no convincing advantage of the recombinant preparations compared to the highly purified or original urinary preparations that justify the higher cost of rhFSH (2).
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