Women with Trisomy X (TXS) appear to be at increased risk for premature ovarian insufficiency (early menopause and loss of fertility); however, very little research on this relationship has been conducted. The objective of this study was to compare ovarian function, as measured by anti-mullerian hormone (AMH) levels, between girls with and without TXS (median ages 13 and 15 years, respectively). AMH blood levels were compared between these groups. Females with TXS had lower AMH levels compared to females without TXS. Lower AMH levels in females with TXS may represent an increased risk for early menopause in these patients and potentially a window of opportunity to pursue fertility preservation options. Additional research is needed to understand the natural history of low AMH levels and future risk of early menopause in girls with TXS.