Developments in human recombinant follicle stimulating hormone technology: are we going in the right direction?

Recent developments in recombinant DNA technology have enabled the large scale production of human recombinant follicle stimulating hormone (rFSH); and this compound has recently been introduced to the market. Understanding of the structure-function relationship of FSH isohormones is crucial in understanding discussions on the standardization procedures of gonadotrophin preparations, potential differences in clinical efficacy of the various gonadotrophin preparations and in comprehending future developments (long-acting and short-acting forms, and rFSH preparations with altered isohormone profiles). Differences between immunoreactive and bioactive serum FSH concentrations have been observed following the administration of rFSH. Accordingly, the isohormone distribution of rFSH is similar to, but not identical with, natural human FSH. Issues relevant to daily practice discussed in this review include: the total absence of urinary contaminants allowing for the safe s.c. administration of the compound. Production is independent from urine, and the capacity can be adjusted according to clinical needs. The relationship between serum oestradiol concentrations and number and size of follicles observed by ultrasound may change when rFSH is combined with gonadotrophin-releasing hormone (GnRH) agonist, due to low serum lueinizing hormone (LH) concentrations. In the case of endogenous serum LH concentrations within the normal range, exogenous administration of LH is redundant. In the near future, rFSH preparations with altered bioactivity will be available.