ABSTRACT
Clomiphene citrate (CC) is a non-steroidal selective estrogen receptor modulator (SERM) that consists of two stereoisomers which have tissue-specific estrogen agonist and antagonist actions. It is widely used to stimulate ovulation by interfering with the estrogen negative feedback mechanism on the pituitary gland. While its antagonism of estrogen action at the level of the hypothalamus and pituitary results in elevated follicle-stimulating hormone (FSH) levels and therefore stimulates follicle development in the ovary, it also acts as an estrogen antagonist in the endometrium, where it may have negative effects upon endometrial development, receptivity to embryo implantation, and pregnancy. The potential clinical effect is an increase in pregnancy rate, but a smaller increase than that which would be predicted by the magnitude of the increase in the number of follicles which reach ovulation.1-3 Investigators have used a variety of diagnostic
methods to attempt to better study the effects of clomiphene citrate upon the endometrium, although it is important to remember that the only important outcome of interest is successful pregnancy.
