Expansion of a CGG trinucleotide repeat in the 5’UTR of the FMR1 gene (encoding FMRP) beyond 200 repeats results in fragile X syndrome, but around 20% of women with 55–200 repeats (known as premutation alleles) display a condition known as fragile X-associated premature ovarian insufficiency (FXPOI) (Sherman, 2000, Sherman et al., 2014, Mailick et al., 2014). Here, FMR1 is linked to fragile X syndrome.