The 'normal' range of FMR1 triple CGG repeats may be associated with primary ovarian insufficiency in China

The aim of this study was to investigate the relationship between normal Fragile X mental retardation gene 1 (FMR1) CGG repeat numbers and primary ovarian insufficiency (POI) occurrence or subsequent resumption of ovarian function. A total of 122 women with POI and 105 controls were followed up and analysed in our centre. The prevalence of premutation and intermediate range of FMR1 CGG repeats in Han Chinese women with POI was only 0.81% (1/122) and 1.64% (2/122), respectively. The risk of POI occurrence for less than 26 CGG repeats and 29 or more CGG repeats in allele1 (smaller allele) was significantly higher than that for 26-28 CGG repeats (odds ratio 13.50, 95% confidence interval: 3.21 to 56.77 and 6.32, 95% confidence interval: 2.49 to 16.09 respectively; both P < 0.001). No significant difference was found in the CGG repeat distribution (<26, 26-28, or ≥29) in FMR1 allele1 between POI cases whose ovarian function resumed and those whose ovarian function did not. It is suggested that the CGG repeat number in allele1, but not that in allele2 (longer allele), was significantly associated with POI occurrence (P < 0.001). Fewer than 26 or more than 28 CGG repeats in FMR1 allele1 were both risk factors of POI occurrence.