[Evaluation of genetic factors in the variability of menarche]

The purpose of the study was to assess the correlation of menarche and the similarity of other features of pubertal development at the onset of menarche in sisters compared to girls which are not in kinship. The longitudinal study was performed in school girls in the city of Osijek. Seventy-four pairs of sisters i.e. 148 girls aged 9 to 15 years in which the menstrual cycle had not started were embraced. The "nonrelated pairs" were formed within the same group of girls. Results showed the significant intrapair correlation of menarcheal age between sisters whereas the correlation in nonrelated pairs did not exist. The body height at the onset of menarche in both groups of pairs--sisters and nonrelated girls--was positively correlated, but significance was on higher level in sisters. Body weight varied in a large range; the intraclass correlation being significant in pairs of sisters only. Menarche appeared in almost equal distribution of breast stage as it was found in other studies. However, breast stage showed considerably higher concordance in sisters than in the nonrelated pairs. The pubic hair stage at menarche also showed higher similarity in sisters which speaks in favour of genetic influence on mutual relationship of certain sequences in pubertal development. Results confirm that age of menarche as well as the total, complex course of pubertal development are under high influence of genetic factors.