The role of steroid hormones in ART.

Steroid hormones hold a major role in female fertility and their proper utilisation and monitoring in modern assisted reproduction protocols is important. Oocyte maturation and endometrial receptivity are the two major factors that appear to be related to a successful outcome in Assisted Reproductive Technology (ART). Many reports suggest that oocyte immaturity accounts for a considerable loss of efficiency in ART, mainly due to the poor quality of the obtained embryos and their inability to develop normally. Oestrogen appears to exert its effects on the cytoplasmic maturation of the oocyte, while progesterone has been shown to accelerate meiotic resumption. Moreover, ovarian stimulation appears to affect the normal luteal function and shifts in the window of implantation as a response to hormonal supplementation have also been observed. The ethical limitations in conducting in vivo studies of human implantation, have led to an indirect hormonal- and morphologic-oriented assessment of endometrial receptivity. The two main protocols of luteal support involve either progesterone supplementation or hCG administration, whereas the combined supplementation with oestradiol remains controversial. This brief review aims to summarize the current knowledge on steroidal actions during the above processes and to address their potential use in the improvement of current ART protocols.