PHARMACOKINETICS OF FOLLICLE-STIMULATING-HORMONE - CLINICAL-SIGNIFICANCE

Objective: To review studies that examine the pharmacokinetics and pha rmacodynamics of endogenous, as well as several exogenous FSH preparat ions. Design: Related studies were identified through a computerized b ibliographic search. Patients: initial pharmacodynamic studies were do ne in animal models and in women and men with either hypogonadotropic hypogonadism or suppressed hypothalamic-pituitary- gonadal axis. More recent studies evaluated FSH pharmacokinetics during ovulation inducti on treatment in women with normal ovulatory cycles or polycystic ovari an syndrome. Results: Various types of FSH exist according to their si alic acid content. High estrogen levels induce the secretion of less s ialylated molecules with higher receptor affinity and an increased cle arance rate. It appears that there is a threshold FSH level that shoul d be reached to achieve an ovarian response. A very narrow range exist s between the threshold and ceiling level for monofollicular growth Th is threshold level is surpassed intentionally during IVF treatment cyc les to induce multiple follicular recruitment. The threshold level can change under situations such as polycystic ovaries, perimenopause, or al contraceptives, and GnRH analogue treatment. Conclusions: To avoid the risk of ovarian hyperstimulation syndrome and multiple pregnancies , careful adjustments of serum FSH levels should be made by fine dosag e modifications, By monitoring FSH levels and using less sialylated pr eparations, the efficacy of the treatment probably will improve.