ABSTRACT
This chapter analyzes the physiologic principles upon which the use of gonadotropins for clinical purposes is based. A basic knowledge of gonadotropic control of ovarian function is an essential requirement for a proper understanding of ovulation-induction techniques using exogenously administered gonadotropins. The three gonadotropins involved in ovulation induction (follicle stimulating hormone (FSH), luteinizing hormone (LH), and human chorionic gonadotropin (hCG)) are now commercially avail-able and produced in vitro by recombinant DNA technology. This results in reliable supply, high batch-to-batch consistency, high purity, absence of contaminating human proteins, likelihood of reducing the risk of infectious particles, and elimination of drugs co-extracted from urine, which is collected from numerous donors. These highly specific monohormonal products have permitted important advances in our understanding of gonadotropin action at the cellular level, and have also provided us with the perspective of preparing consistent-formulation regimens for ovulation induction or tailoring therapy with FSH and LH, individually or combined, according to the individual patient’s needs. Thus, recombinant human FSH (rhFSH) has proved to be more efficacious and/or efficient than urinary FSH for ovulation induction in polycystic ovarian syndrome (PCOS) patients and inducing multiple follicular development in pituitary-suppressed women undergoing assisted
reproductive techniques (ART). rhFSH in combination with rhLH has also resulted in effective stimulation of follicular growth in World Health Organization (WHO) group I anovulation. Interestingly, preliminary data suggest that high-dose rhLH, in association with rhFSH, administered in the late follicular phase, may induce atresia of secondary follicles while supporting the growth of a dominant follicle to preovulatory conditions in both WHO type I and type II anovulation. Recent data indicate that rhLH used for induction of follicular maturation and early luteinization in women undergoing superovulation with rhFSH for ART is a more physiologic surrogate surge than urinary hCG, and thus would be beneficial in terms of reducing the risk of ovarian hyperstimulation syndrome (OHSS). Finally, rhCG is a safe and effective agent in triggering ovulation, and may prove to be a more reliable ovulation-inducing agent than urinary hCG.
