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.     

Nongenomic actions of steroid hormones

Steroid hormones modulate many physiological processes. The effects of steroids that are mediated by the modulation of gene expression are known to occur with a time lag of hours or even days. Research that has been carried out mainly in the past decade has identified other responses to steroids that are much more rapid and take place in seconds or minutes. These responses follow nongenomic pathways, and they are not rare.     

Time-resolved fluoroimmunoassay of steroid hormones

The use of europium chelates as labels in immunoassays and their sensitive quantitation based on time-resolved fluorescence is reviewed. The technique is applied on competitive solid-phase immunoassays for direct determination of progesterone and estradiol in serum samples. Both antigen- and antibody-labelled competitive assays are described. The nonisotopic label technology, which provides a very high specific activity, as well as the antibody-labelled competitive assays, present several advantages in the assay of haptens as e.g. steroids. As the optimal sensitivity of competitive methods is not limited by the specific activity of the label the steroid assays which employ europium chelates as labels do not show any marked increase in sensitivity as compared to that achieved by using 125I. The potential sensitivity provided by the high specific activity of the label is optimally utilized in noncompetitive immunometric assays.     

The analysis of interaction of lipoproteins and steroid hormones

Using the methods of gel-filtration and fluorescence quenching, it has been demonstrated that plasma lipoproteins bind steroid hormones and can therefore play a role in their active transport in the body. High density lipoproteins demonstrate the highest affinity for steroids.     

Regulation of apoptosis by steroid hormones

Steroid hormones play major roles in regulation of growth, development, homeostasis, and cell death. Together with other hormones and growth factors, steroids regulate both the function and cellular composition of organs throughout the body. In this article we will discuss the mechanisms of steroid hormone regulated apoptosis. Emphasis will be placed on the effect of glucocorticoids on lymphoid cells.     

Synthesis of 13C-labeled steroid hormones

The synthesis of 13C-labeled steroid hormones is reviewed. Two general approaches are highlighted: partial synthesis in which part of the steroid nucleus is replaced with 13C-labeled synthons, and total synthesis. Examples from both approaches, leading to (3-(3)C)-, (4-(13)C)-, (3,4-(13)C2)-, and (1,2,3,4-(13)C4)- labeled steroid hormones (e.g., testosterone, estradiol, progesterone, and cortisol), are presented.