Girls whose transition into puberty is initially marked by breast development are heavier, have more body fat and begin menstruating at an earlier age than those whose first sign of puberty is pubic hair, a 10-year study has found. Since both obesity and early menarche increase the risk factors for breast cancer, such girls may have a higher cancer risk later in life.

Researchers at the Children's Hospital Medical Center in Cincinnati studied 859 girls. Among the girls who developed signs of puberty before age 12, the first sign in two of three was breast development. These girls also were more likely to be heavier and have more body fat in the year before puberty, as well as at ages 18 and 19, than those whose first indicator was pubic hair.

The common biological thread between obesity, early breast development, early menstruation and increased risk of breast cancer may be hormonal. Lead researcher Dr. Frank Biro said the girls may have an increase in estrogen production compared to androgens, or they may be more sensitive to the effects of estrogen. The study was published in the June issue of the Journal of Pediatrics.

Copyright 2003 Los Angeles Times