Does handedness and altitude affect age at menarche?

Although there is knowledge about earlier mean age at menopause among left-handed postmenopausal women, it is unclear from the literature whether age of menarche is influenced by the prenatal hormonal pattern and cerebral lateralization. We therefore planned to investigate the relation between age of menarche and cerebral lateralization in girls at an altitude of nearly 2000 m. Sixty-two girls, aged between 9.4 and 15.5 years, were interviewed by questionnaire about manual dominance and menarcheal age. All girls were divided into two groups: left-handers (n = 31) and right-handers (n = 31). It was shown that there was a significantly lower average age of menarcheal appearance (12.96 +/- 1.34 years) in the left-handers' compared with the right-handers' (13.72 +/- 1.41 years; p = 0.025). The earliest menarcheal age was 9.4 years in left-handers and 10.1 years in right-handers.A menarcheal age of 13.34 +/- 1.35 years was found for the whole group at an altitude of nearly 2000 m. This data leads us to believe the existence of a link between functional brain asymmetry and menarche. It would appear that the activation of the hypothalamic-pituitary-gonadal axis is earlier in left-handed females than in right-handed females.