## 4 Discussion  
_GPR30_ is a transmembrane receptor that induces rapid non-genomic responses upon E2 stimulation. Along with classical E2 receptors, evidence suggests that _GPR30_ has  
Figure 4: The association between _GPR30_ mRNA abundance in spermatozoa and pregnancy. The figure shows the association of _GPR30_ mRNA abundance in spermatozoa with biochemical pregnancy, \(n=28\). (**A**) Serum \(\beta\)-HCG concentrations were collected from women who were reported to achieve a biochemical pregnancy after embryo transfer. The association between _GPR30_ mRNA expression and serum \(\beta\)-HCG concentration was evaluated by computing the Pearson correlation coefficients (\(t\)), assuming a Gaussian distribution (confidence interval of 95%). Correlations between the studied parameters were not found to be statistically significant. (**B**) From a total of 60 embryo transfers, 28 women were classified as biochemically pregnant. The remaining 32 women did not become pregnant after embryo transfer. Results are expressed as the mean \(\pm\) standard error mean (biochemical pregnancy mean = 1.63 \(\pm\) 0.27 arbitrary units, \(n=28\); no pregnancy mean = 1.13 \(\pm\) 0.17 arbitrary units, \(n=32\)), \(p=0.0262\). (**C**) Of these, 22 women were reported to be clinically pregnant. The remaining 36 women had not become pregnant after embryo transfer or had a spontaneous abortion. Results are expressed as mean \(\pm\) standard error mean (clinical pregnancy mean = 1.68 \(\pm\) 0.33 arbitrary units, \(n=22\); no pregnancy mean = 1.13 \(\pm\) 0.16 arbitrary units, \(n=36\)). Statistical analysis was performed with a two-tailed Student’s \(t\)-test for parametric data (confidence interval of 95%). Values of * \(p<0.05\) were considered to be statistically significant. a crucial role regarding the testis, where it appears to participate in the regulation of the proliferation/apoptosis balance of germ cells [30], along with the downregulation of steroidogenesis [31]. The work performed by [PERSON] and colleagues further confirmed the importance of the _GPR30_ role for the testis, by proposing that this receptor could be responsible for the modulation of the detrimental effects of excess E2 on the testis of Klinefelter individuals [32]. However, the role of _GPR30_ in spermatozoa remains to be elucidated. We hypothesized that the _GPR30_ transcript was present in human spermatozoa and that its abundance in spermatozoa could be related to the fertility potential of males and have an impact on the outcome of ART. A previous study proposed that _GPR30_ can modulate the E2 effects on immature rat epididymal epithelium cells [33]. The authors, [PERSON] and colleagues, hypothesized that the role of _GPR30_ on the epididymal cells could be essential for sperm maturation [33]. Nonetheless, in our population, sperm quality was not correlated with _GPR30_ mRNA abundance in spermatozoa. From a different viewpoint, the present study likewise could not establish any correlation between paternal BMI and _GPR30_ mRNA abundance in spermatozoa. Pateral age was also not correlated to _GPR30_ mRNA abundance in spermatozoa, even though the strong hormonal dysregulation found in older men is known to have severe detrimental effects on male fertility potential in general [28; 34]. However, our results suggest that the _GPR30_ transcript may not have an important role in the modulation of E2 effects on human spermatozoa formation nor on maturation. Some evidence suggests that the _GPR30_ transcript may be important for pregnancy, specifically during embryo implantation. A study performed by [PERSON] and colleagues reported that the stimulation of _GPR30_ with E2 induces a rapid Ca\({}^{2+}\) intracellular flux in mouse blastocyst cells. This stimulation promoted the implantation of the mouse blastocysts in a uterine epithelial cell line (Ishikawa cell line) [35]. Furthermore, _GPR30_ appears to be important in the regulation of proliferation/apoptosis balance between trophoblast cells (the cells forming the outer layer of the blastocyst) [36].