The genetic contribution to pubertal growth and development studied by longitudinal growth data on twins.

Forty-eight pairs of MZ and like-sex DZ twins of Panjabi parentage were studied longitudinally for such pubertal changes as growth of genitalia, pubic, axillary and facial hair, change of voice and ejaculation of semen in boys, and growth of pubic and axillary hair, breast development and onset of menarche in girls, besides growth in height and weight. Mean intra-pair age differences are small and intra-pair correlations for age at different secondary sexual developments are higher in MZ twins than in DZ twins in both sexes. Mean intra-pair differences and intra-pair correlations for the time taken to pass from first stage to the final stage of development also present a similar picture. Intra-pair height and weight differences and differences in their growth velocities also indicate that MZ twins are more concordant than DZ twins throughout the adolescent growth period. These findings indicate a strong genetic component in regulating the pubertal changes as well as in the growth of height and weight in the two sexes. The role of environmental factors in at least some of the pubertal changes is also indicated.