The age of menarche may be subject to hereditary influences but the specific determinants are unknown. Our aim was to investigate the possible association of a functional (TAAAA)n polymorphism in the promoter of the sex hormone-binding globulin (SHBG) gene with the timing of menarche. This polymorphism has been associated with polycystic ovary syndrome (PCOS) and is considered to contribute to SHBG levels. We studied 130 healthy normal-weight adolescent females from a closed community in North-Western Greece. Information on menarche was obtained through interviews. The BMI was recorded. Genomic DNA was isolated from peripheral blood leukocytes for genotyping the TAAAA repeat region. We subdivided our subjects into two groups based on median age of menarche: those with menarche <13 years and those with menarche > or =13 years. Genotype analysis revealed six (TAAAA)n alleles containing 5-10 TAAAA repeats. The distribution of alleles was different in the two groups. Girls with late menarche had more frequently longer TAAAA alleles (>8 repeats), while girls with early menarche had shorter alleles at a greater frequency (P=0.048). The major contribution to early menarche was by the 6 TAAAA repeat allele. Furthermore, carriers of the longer allele genotypes had later menarche (13.24+/-1.15 years) than those with shorter allele genotypes (12.67+/-1.15, P=0.018). These findings provide evidence for a genetic contribution of SHBG gene to the age of menarche.