The (TTTA)n polymorphism of aromatase (CYP19) gene is associated with age at menarche

Twin studies have shown that age at menarche may be subject to hereditary influences but the specific determinants are unknown. Estrogens are known to have an important role in menarche. Since the enzyme aromatase is responsible for the conversion of androgens to estrogens, the aromatase (CYP19) gene could be a candidate gene for the regulation of menarche. The aim of this study was to investigate the possible association of the CYP19(TTTA)(n) polymorphism with age at menarche.

We studied 130 healthy adolescent females from a closed community in North-Western Greece. Information on menarche was obtained through interviews. The BMI was recorded. The CYP19(TTTA)(n) polymorphism was genotyped.

The mean age at menarche was 12.9 ± 1.2 years and the BMI = 19.8 ± 2.3 kg/m(2). Genotype analysis revealed 5 CYP19(TTTA)(n) alleles containing 7-11 TTTA repeats. Girls homozygous for the allele with 7 TTTA repeats had earlier menarche (12.45 ± 0.9 years) than girls carrying other genotypes (13.0 ± 1.2 years, P = 0.025), whereas the BMI was not different between these two subgroups. Carriers of the allele with 11 TTTA repeats had later menarche compared with non-carriers (14.1 ± 0.75 versus 12.8 ± 1.2 years, P< 0.001), whereas no difference was found in BMI values. Comparing girls with early menarche (<12 years, 25th percentile) with girls with late menarche (>13.75 years, 75th percentile), we found that 31% of the girls with early menarche were homozygous for the (TTTA)(7) allele compared with 6.9% among girls with late menarche (P = 0.018). In addition, none of the girls carrying the (TTTA)(11) allele was found among the subgroup with early menarche, whereas 24.1% of girls with late menarche had the (TTTA)(11) allele (P = 0.001). No association between other alleles and age at menarche was found.

There is evidence for a genetic contribution of the CYP19 gene to the age at menarche.