Reduced levels of oestrogen receptor β mRNA in Swedish patients with chronic fatigue syndrome

Background: Chronic fatigue syndrome (CFS) is an illness with unknown aetiology and pathophysiology. The difference in incidence by sex observed for CFS indicates a role for oestrogen and oestrogen receptors in disease development. Furthermore, an immunomediated pathogenesis has been suggested for CFS, providing an additional connection to oestrogen, which displays immunomodular functions. Aims: To investigate a possible association of oestrogen receptor (ER) mRNAs and two ER beta single-nucleotide polymorphisms (SNPs) with CFS. Methods: Messenger RNA levels of ER alpha, ER beta wt and ER beta cx were investigated in peripheral blood mononuclear cells from 30 patients with CFS and 36 healthy controls by quantitative real-time polymerase chain reaction. Two ERb SNPs were scored in the same material. Results: The CFS group showed significantly lower mRNA expression levels of ERb wt compared with the healthy control group. No differences were observed for ERa or ERb cx between patients and controls. There were no significant differences in frequency for the investigated ERb SNPs between cases and controls. Conclusions: The reduced ERb wt expression level observed in this study is consistent with an immunemediated pathogenesis of CFS. Additionally, the observation that ERb wt expression is decreased in CFS could provide an entry point to identify interesting, potentially disease-causing, candidate molecules for further study. A possible connection between oestrogen, oestrogen receptors and CFS should be evaluated further.