*2.2. Clinical Samples*

Skin biopsies for LC–MS/MS study were obtained from 5 healthy volunteers (MS volunteers), namely 2 males and 3 females between the ages of 39 and 79 years (mean age: 61.6 years), and from an equal number of psoriasis patients (MS patients), namely 3 males and 2 females between the ages of 30 and 68 years (mean age: 49.2 years). Skin biopsies for qPCR and ELISA assays were obtained from female participants: 20 psoriasis patients and 11 healthy volunteers that we identified as qPCR/ELISA participants. To distinguish the changes in gene expression caused by the disease from ones caused by menopause, the participants were divided in four groups. The first group included 10 patients without menopause between the ages of 19 and 43 years (mean age: 31.5 years). The second group included 10 patients with menopause between the ages of 46 and 54 years (mean age: 50.2 years). The third group included 6 healthy volunteers without menopause between the ages of 26 and 38 years (mean age: 31 years). The fourth group included 5 healthy

volunteers with menopause between the ages of 43 and 57 (mean age: 50.8 years). The additional details on participants of this study can be found in Table 1.

**Table 1.** Clinical characteristics of psoriasis patients and volunteers that participated in the LC– MS/MS, qPCR, and ELISA studies.


The patients that participated in our study discontinued topical treatment for 1 week prior to the biopsy collection (2 week in the case of systemic therapies). Each patient donated two 4 mm punch biopsies of lesional and uninvolved skin following a local anesthesia. Biopsies of uninvolved skin were taken at least 6 cm away from the nearest skin lesion. The collected biopsies were flash frozen in liquid nitrogen and stored at −80 ◦C until processing. Blood (3 mL) was withdrawn by venipuncture without anticoagulant at day 3 or 4 of the menstrual cycle. Serum was separated, divided into aliquots, and stored frozen at −20 ◦C until needed.
