Boys and girls may go through puberty sooner if their mothers and fathers were early bloomers, a recent Danish study suggests.
Researchers studied the timing of puberty for 672 girls and 846 boys relative to their parents and found kids who developed pubic hair and other hallmarks of adulthood at an unusually young age tended to have mothers and fathers who also matured early.
"Both genetic and environmental factors undoubtedly influence puberty timing," said lead study author Dr. Christine Wohlfahrt-Veje, a growth and development researcher at the University of Copenhagen.
"Our study shows that both boys and girls inherit from both mothers and fathers, but indicates that the early pubertal markers - onset of breasts and pubic hair - in girls are less dependent on genetic and hence more on environmental factors such as childhood growth patterns and possibly other environmental exposures," Wohlfahrt-Veje added by email.
Children who go through early puberty may be shorter than average adults because after their early growth spurt their bones may stop growing at a younger age, and they are also at increased risk of obesity as adults. During adolescence, they may face an increased risk of social and emotional problems and earlier sexual experiences.
Some recent research points to earlier puberty onset in general, especially in girls in developed countries. Environmental factors like diet, obesity and chemicals that mimic human hormones have all been suspected of playing a role.
To look at the contribution of genetics to puberty timing, Wohlfahrt-Veje and colleagues examined medical records from annual checkups kids received between 2006 and 2013 as well as data on parental puberty timing from questionnaires completed by their parents.
When fathers matured early, boys tended to develop pubic hair almost one year ahead of boys with fathers who went through puberty late. Sons of men who developed early also grew enlarged testes about 9.5 months sooner than sons of fathers who went through puberty late.
Girls with fathers that matured early started menstruating about 10.5 months sooner than girls with late-bloomers for fathers, and the girls of fathers who went through early puberty also developed pubic hair around 7 months before girls whose fathers developed late. Early breast development in girls, however, didn't appear to be tied to early puberty in their fathers.
When mothers went through puberty early, their sons and daughters tended to follow suit.
Daughters of women who matured early typically started menstruating about 10 months sooner than girls with late-blooming mothers.
Sons of women who went through puberty early typically went through genital maturation about 6.5 months before boys with mothers who developed late.
One shortcoming of the study is that researchers relied on parents to accurately recall and report on when they went through puberty many years earlier. They also got more data from mothers than fathers, which may have affected the relative influence of each parent in the results.
Because the study didn't find as strong an association with parental puberty timing and breast development in girls, this suggests that other factors beyond genetics may influence puberty in girls, the authors conclude in the Journal of Clinical Endocrinology and Metabolism.
"A broad normal variation exists within timing of puberty," Wohlfahrt-Veje noted.
Still, when kids develop early, they quite likely came from a long line of early bloomers.
"A large proportion of this variation seems to be explained by genetics," Wohlfahrt-Veje added. "If either the mother or father had early or late pubertal development it is likely to influence the timing of pubertal onset in both their sons and daughters."