*2.8. Statistical Analysis*

Due to small sample size, the data of LC–MS/MS were analyzed with non-parametric statistics using the Mann–Whitney U test. The Mann–Whitney U test was also used to evaluate gender-related differences in protein expression. Data variability was analyzed in R using the "prcomp" function. Two-sided unpaired Student's *t*-test was used to analyze the data of the qPCR and ELISA studies that were performed on larger groups of participants. In all cases, differences were considered statistically significant when *p* < 0.05.

#### **3. Results**

## *3.1. The Blood of Female Psoriasis Patients Contains Less Estradiol and Progesterone, and More Testosterone Compared to the Healthy Volunteers*

The analysis of blood samples (Figure 1) revealed significant differences in the levels of sex hormones between qPCR/ELISA psoriasis patients (n = 20) and qPCR/ELISA healthy volunteers (n = 11). The levels of E2 and PG were significantly higher in healthy volunteers (*p* = 0.042 and 0.001, respectively). In contrast, the level of TS was significantly higher in patients (*p* = 2 × 10−<sup>4</sup> ). In turn, the blood of participants with menopause, being either healthy volunteers or patients, contained less E2 and PG but more TS compared to their normally menstruating counterparts (Table 3).

**Figure 1.** The levels of sex hormones in the blood of psoriasis patients and healthy volunteers that participated in the qPCR and ELISA experiments. The following individuals participated in these experiments: psoriasis patients without menopause (n = 10); psoriasis patients with menopause (n = 10); healthy volunteers without menopause (n = 6); and healthy volunteers with menopause (n = 5). \* *p* < 0.05 when patients compared to healthy volunteers.

*–* **Table 3.** The levels of sex hormones in blood samples of qPCR/ELISA participants with and without menopause. pM and nM are concentrations (pmol/L and nmol/L, respectively).

