Functional brain asymmetry, handedness and menarcheal age

Functional brain asymmetry influences many functions of the organism; the neuroendocrine axis is one that has received insufficient attention. In this study we set us as the goal of studying the link between functional brain asymmetry and menarcheal age in females with left versus right manual dominance. The appearance of the first menarche was used as a natural model of functioning of the hypothalamic-pituitary-gonadal (HPG) axis. 1695 females, aged between 16 and 25 years, were interviewed by questionnaire about manual dominance and menarcheal age. 182 women were selected and divided into 2 groups: all left-handers (n = 91), and a control group of 91 right-handers. We found a significantly lower average age of menarcheal appearance in the left-handers' age of 12.09 +/- 0.16 years compared to the right-handers' age of 13.32 +/- 0.12 years (p < 0.001). The earliest menarcheal age in left-handers was 8 years and the peak of appearance at age 13 (in 30.76% of the cases). In right-handers these values were 10 and 14 years (in 40.60% of the cases), respectively. The data allow us to accept the existence of a link between functional brain asymmetry and menarche, which causes earlier activation of the HPG axis in left-handed females.