The significance of fragile X mental retardation gene 1 CGG repeat sizes in the normal and intermediate range in women with primary ovarian insufficiency.

STUDY QUESTION: Are fragile X mental retardation gene 1 (FMR1) CGG repeats in the normal and intermediate range (up to 55 repeats) associated with primary ovarian insufficiency (POI) in a large case-control study? SUMMARY ANSWER: No association was found between CGG repeats of intermediate size and POI compared with controls. WHAT IS KNOWN ALREADY: CGG repeats in the FMR1 gene in the premutation range (55-200 repeats) have consistenly associated with POI. Intermediate range CGG repeats have been considered for a potential association with POI. STUDY DESIGN, SIZE: A case-control study in 375 well-phenotyped Dutch women diagnosed with POI and 3368 controls with natural menopause ≥40 years of age. PARTICIPANTS/MATERIALS, SETTING, METHODS: The FMR1 CGG repeat number was determined by PCR amplification in women diagnosed with POI and women with a known age at natural menopause ≥40 years. The prevalence of intermediate sized CGG repeats (45-54 repeats) was compared between POI cases and controls using Fisher's exact test. Differences in mean CGG repeat lengths on allele 1 and allele 2 between POI cases and controls were tested using analysis of variance. MAIN RESULTS AND THE ROLE OF CHANCE: The frequency of intermediate sized CGG repeats on the allele with the longest triple repeat number was not statistically significantly different between POI cases and controls (2.7 and 3.8%, respectively, odds ratio 0.72, 95% confidence interval: 0.38-1.39, P = 0.38). In women with POI, linear regression analysis for age at POI diagnosis and CGG repeat size also failed to show any association (ß = -0.018, P = 0.74). LIMITATIONS, REASONS FOR CAUTION: FMR1 CGG repeat lengths in POI cases and controls were genotyped in two different laboratories. The distributions of CGG repeats may vary among the different ethnic populations in our study. Also, in our study women with primary amenorrhea (N = 17) were included in the POI group. WIDER IMPLICATIONS OF THE FINDINGS: We found no association between intermediate sized CGG repeats and POI compared with controls. Therefore, a role for FMR1 CGG repeat sizes up to 55 repeats in the ovarian ageing process may be questioned. Moreover, there seems limited value in the evaluation of normal- and intermediate FMR1 repeat size in the diagnostic work-up of women affected by POI, or for prognostic purposes in women at risk of developing POI. STUDY FUNDING/COMPETING INTERESTS: The Prospect-EPIC study was funded by 'Europe Against Cancer' Program of the European Commission (SANCO); the Dutch Ministry of Health; the Dutch Cancer Society; ZonMW the Netherlands Organization for Health Research and Development; World Cancer Research Fund (WCRF) and the Dutch Heart Association.

The association of CGG repeats in the FMR1 gene and timing of natural menopause.

STUDY QUESTION: Is there an association between the number of CGG repeats in the FMR1 gene in the normal and intermediate range and age at natural menopause? SUMMARY ANSWER: The number of CGG repeats in the normal and intermediate range in the FMR1 gene was not associated with age at natural menopause. WHAT IS KNOWN ALREADY: Excessive triple CGG repeats in the FMR1 gene have been widely associated with primary ovarian insufficiency. Recently, the number of CGG repeats in the normal and intermediate range (up to 55 repeats) was found to be associated with serum levels of anti-Müllerian hormone and follicle-stimulating hormone, as markers for ovarian ageing. This suggests that repeats in the normal and intermediate range could be involved in the rate of exhaustion of the ovarian primordial follicle pool and ultimately the timing of menopause. STUDY DESIGN, SIZE: Cross-sectional study in a population-based sample of 3611 Caucasian women with natural menopause. PARTICIPANTS/MATERIALS, SETTING, METHODS: The FMR1 CGG repeat number was determined by PCR amplification in 3611 women with a known age at natural menopause. A possible relation between CGG repeats in the normal and intermediate range (up to 55 repeats) and menopausal age were analysed in various ways, including linear regression analysis and analysis of variance. MAIN RESULTS AND THE ROLE OF CHANCE: The number of CGG repeats in the normal and intermediate range in the FMR1 gene was not associated with age at natural menopause. The mean age at menopause was 50.30 (± 4.2) years for women with <45 repeats and 50.64 (± 3.4) years for women with intermediate-sized repeats (P = 0.37). Linear regression analysis of the number of CGG repeats showed no association with menopausal age (ß = 0.019, P = 0.16). LIMITATIONS, REASONS FOR CAUTION: In our cohort, age at menopause was self-reported and determined retrospectively. WIDER IMPLICATIONS OF THE FINDINGS: Earlier observations suggesting that the number of CGG repeats in the normal and intermediate range is associated with the individual variation of the ovarian ageing process could not be confirmed in the current, large sample size study. A relation between the number of CGG repeats in the normal and intermediate range and age at natural menopause appeared to be absent. This finding questions the role of CGG repeat sizes in the ovarian ageing process.