The effect of exogenous gonadotropic hormones on the endometrium of the rat

This investigation examined the effects of hyperstimulation on the uterine endometrium of rats. Female rats were injected, out of cycle, with FSH followed by hCG and mated. Control rats were mated during oestrus. Animals were killed at 5.5 days of pregnancy. The endometrium was examined by light and electron microscopy. Hyperstimulation resulted in an increase in the length and number of microvilli and a deficiency of the glycocalyx of surface epithelial cells. Stromal cells failed to undergo decidualization. These alterations in morphology may interfere with attachment and implantation of the embryo.