BACKGROUND: This study aimed to investigate serum inflammatory factor levels of polycystic ovary syndrome (PCOS) in female patients with bipolar disorder (BD) to explore the related inflammatory molecular mechanisms preliminarily. METHODS: The study recruited 72 female drug-naïve patients with BD and 98 female healthy controls (HCs). Demographic information, menstrual cycles, sex hormone levels, and ovarian ultrasound data were collected from them. Additionally, their serum inflammatory factor levels and the proteomics of peripheral blood mononuclear cells were analyzed. RESULTS: The levels of interleukin (IL)-8 and IL-13 were significantly higher in patients with BD than in HCs (p <
0.05), and the IL-8 level was higher in BD patients with PCOS than in those without (adjusted p = 0.07). Bioinformatics analysis revealed that downregulated genes with significant differences between the two groups were all involved in immune-inflammatory-related pathways, and the expression of downregulated genes BTN3A2, MAP2K5, JCHAIN-B, and DMAP1 showed substantial differences and consistent trends between the two groups. CONCLUSION: IL-8-related chronic inflammatory response is closely associated with PCOS in BD patients, and genes such as BTN3A2 may mediate this chronic inflammatory response by negatively regulating the abnormal differentiation of T helper 17 cells, serving as one of the mechanisms underlying its pathogenesis.