## 4 Discussion
In our study, we assessed the levels of miR-320-5p, a member of the miR-320 family that had not been investigated in PCOS so far. MiR-320-5p (and miR-320) has been described as a tumor suppressor, affecting cell proliferation and migration [29]. In PCOS, a significant proliferation rate and low apoptotic rate of granulosa cells are associated with abnormal folliculogenesis, leading to anovulation [30]. In the current study, miR-320-5p was significantly up-regulated in PCOS patients compared to healthy controls (\(p=0.0006\)). It also showed a trend of overexpression in the PCOS group compared to the HAC group (\(p=0.079\)). In the PCOS group, miR-320-5p correlated with the systolic blood pressure, but we did not find correlations with any of the metabolic parameters, the androgen excess or the PCOS phenotype. MiR-103 has been detected in human blood and granulosa cells and is involved in steroid synthesis, insulin signaling and folliculogenesis [15; 20]. [PERSON] et al. found decreased expression of miR-103 in obese women but increased expression in PCOS patients and a positive correlation with testosterone concentrations [31]. [PERSON] et al. reported decreased expression of miR-103a-3p and a positive correlation with androgen levels in 36 Brazilian women with PCOS [15]. In our study, we investigated miR-103a-5p, which to our knowledge had not been assessed in PCOS patients so far. Like [PERSON] et al., we found significantly increased expression in the PCOS group compared to the healthy controls (\(p\) = 0.0005) but not significant differences in the expression compared to the HAC groups (\(p\) = 0.061) [32]. In the PCOS group, but not in the control groups, miR-103a-5p showed a positive correlation with CRP and, unlike the mentioned above studies, no correlations with other metabolic parameters, androgens and PCOS phenotype. CRP has been validated as a biomarker of an increased cardiovascular risk, equal to increased LDL cholesterol levels [32], and has been found to be increased in PCOS patients in a number of studies [33], including the current one. MiR-194 has been found to be up-regulated in granulosa cells of women with PCOS and in PCOS rat models where it induced apoptosis [23]. [PERSON] et al. in their study, including 65 PCOS women with impaired glucose metabolism, 65 PCOS women with normal glucose metabolism and 45 healthy women, found that miR-194 was overexpressed in women with PCOS and correlated with HOMA-IR [34]. Similar to these results, we found significant overexpression of another miRNA from the miR-194 family. MiR-194-5p was significantly up-regulated in the PCOS patients compared to the healthy control group and showed 65% sensitivity and 81% specificity for diagnosing PCOS. No significant differences in expression compared to the HAC group were found. In the PCOS group, the expression of miR-194-5p correlated with weight, waist circumference and CRP, parameters that are important for cardiometabolic disturbances. These correlations were not found in the control groups. MiR-194-5p was reported to have a regulatory role in different cancers and was proposed as a biomarker for breast cancer [35], but, to our knowledge, has not been assessed or reported in PCOS patients so far. Endometrial cancer (EC) is the second most common gynecologic cancer [24]. Premenopausal women with PCOS have a higher risk of endometrial hyperplasia and EC [1,8]. MiR-15a-5p was found to be significantly up-regulated in plasma and tumor tissue of patients with EC and was identified as a promising biomarker for the early detection of EC. It was also associated with testosterone, which is increased in PCOS, and DHEA-S [24]. These findings determined the choice to study miR-15a-5p. It was significantly upregulated in the PCOS group compared to the two control groups (\(p\) = 0.006 and \(p\) = 0.045, respectively) but displayed higher specificity in distinguishing PCOS patients from healthy controls compared to distinguishing PCOS patients from HAC.