This study investigates the differences in gut and vaginal microbiota between women with premature ovarian insufficiency (POI) and healthy volunteers. POI refers to the reduction in ovarian function before the age of 40, leading to irregular or absent menstruation and decreased estrogen levels, which can significantly affect women's reproductive and overall health. Recent research has suggested that gut microorganisms may influence the balance of steroid hormones through various metabolic pathways. Additionally, certain vaginal bacteria appear enriched in patients with POI, but whether these microorganisms directly impact ovarian function, and how, remains unclear. This study also seeks to address the underexplored role of fungi within the human microbiome. To comprehensively compare differences in gut and vaginal microbiota, the study will recruit 20 women with POI and 20 healthy controls. Both demographic and clinical information will be collected, along with biological samples including blood, urine, stool, and vaginal swabs.