When a girl’s breasts start growing early, it can be a sign she will develop certain diseases later in life. There is evidence of early puberty leading to increased risk of obesity, type 2 diabetes, heart disease and cancer – particularly breast cancer. Girls who develop breasts before the age of ten have around a 20% higher risk of breast cancer in later life than girls who develop breasts between the ages of 11 and 12.
If you could prevent breasts from growing early, you might be able to reduce the girl’s risks of developing these diseases. Until now, unfortunately, scientists have poorly understood the processes that make some girls develop younger than others. But new findings from our research at the University of Glasgow solve a large part of the mystery and could have important health implications as a result.
It is usual for girls to develop breasts around the age of ten, though plenty start earlier or later and this is often seen as normal and harmless. Yet the higher risks of earlier developers ending up with breast cancer or the other diseases are a significant concern, not to mention other psychological and physical problems that can crop up.
In addition to potential feelings of isolation and embarrassment, early puberty is linked to earlier sexual activity, which can lead to emotional damage as well as unwanted pregnancies and sexually transmitted diseases. Studies show correlations with depression and eating disorders; and early developers tend to be tall for their age but actually shorter as adults.
The bad news is that throughout the world, puberty is beginning earlier and earlier. In the US, it is believed to be happening a full year earlier than a few decades ago. However, the reasons are largely unknown.
A number of studies have shown an association with childhood obesity. But while this is a popular theory as obesity is known to affect hormone levels, it does not explain why onset varies substantially between different ethnic and socio-economic groups – earlier among black girls and those from poorer backgrounds. Another theory is that we are increasingly exposed to chemicals in the environment which mimic hormones that may be accelerating puberty.