Last month’s article looked at the scientific method at work in two cases, one of which questioned the methodology of a 1997 study concluding that girls are going through puberty at earlier ages than previously. Now comes the report of another study, partially based on the 1997 one, that produced unexpected results.
Dr. Fred Kadlubar of the U.S. Food and Drug Administration’s National Center for Toxicological Research thought that genetics might play a part in the declining age of puberty in girls. When he heard about a study exploring the possibility that environmental pollutants might be to blame, he asked to collaborate. His hypothesis was that a gene controlling the levels of the female hormone estrogen would be responsible for the onset of early puberty.
To his surprise, Kadlubar reported in March at the annual meeting of the American Association for Cancer Research, he found that a gene that produces a liver enzyme responsible for lowering the body’s level of the male hormone testosterone was responsible. Girls who have the gene break down testosterone as a rate faster than usual. As the testosterone level falls, the level of estrogen relative to testosterone rises.
The beginning of breast development is considered the first sign of puberty. Girls usually begin breast development about a year before they have their first period. The average age of puberty is about 12 for African American girls and 13 for whites.
The earlier girls mature sexually, the longer they will be exposed to estrogen over their lifetimes. Since prolonged exposure to estrogen is associated with an increased risk of developing breast cancer, the presence of this gene could help predict which women have a higher than average chance of developing the disease.