In addition, we assessed the levels of known neurodegenerative disease (glial fibrillary acidic protein and S100 calcium binding protein B) (Petzold et al., 2003; Yardan et al., 2011; Avsar et al., 2012; Michetti et al., 2012) and PMS protein markers (Chitinase 3 like 1 and Chitinase 3 like 2) (Sellebjerg et al., 2017; Hinsinger et al., 2015), correlating protein levels to ccf-mtDNA copies in both PMS cases and controls. The gene discussed is CHI3L1; the disease is premenstrual tension.