The puzzle of why people grow taller and reach puberty earlier than ever can be explained by a sensor in the brain, scientists say.
Average height in the UK increased by 3.9 inches (10 cm) in the 20th century and by up to 7.8 inches in other countries as nutritional health improved.
But how exactly this happens has never been understood.
The discovery could lead to drugs to improve muscle mass and treat stunted growth, say British researchers.
Scientists have long known that people with good nutrition and reliable access to food tend to grow taller and mature faster.
In South Korea, for example, the height of adults has skyrocketed as the nation transformed from a poor country into a developed society. However, in parts of South Asia and Africa, people are slightly taller than they were 100 years ago.
“Make lots of babies”
It is known that signals from food reach a part of the brain called the hypothalamus, telling it about the body’s nutritional health and triggering growth.
This new study, published in Nature, and led by researchers from the University of Cambridge together with teams from Queen Mary University of London, the University of Bristol, the University of Michigan and Vanderbilt University, discovered the brain receptor behind this process.
It is called MC3R and is the critical link between food, sexual development and growth.
“It tells the body that we are ‘wonderful here’, we have a lot of food, so we need to grow up fast, have puberty soon and have a lot of babies,” said Professor Sir Stephen O’Rahilly, study author from Cambridge. .
“It’s not just magic – we have the complete wiring diagram for how it happens.”
When the brain receptor does not function normally in humans, the researchers found that humans tend to be shorter in height and began puberty later than other humans.
The team looked at the genetic makeup of half a million volunteers registered with the UK Biobank – a huge database of genetic and health information – to confirm that this was true.
The children found to have gene mutations that disrupt the brain receptor were all smaller and weighed less than other children, indicating that the effect begins early in life.
The research team found a person who had mutations in both copies of the MC3R gene, which is extremely rare and harmful. This person was very short and started adolescence after the age of 20 years.
But humans are not alone in this – researchers have studied mice to confirm that the same pathway works in animals.
The discovery could help children with severe developmental delays and adolescence, as well as those who become weak with chronic diseases and need to build muscle mass.
Can people continue to grow taller?
There is a cap on height and it is achieved when humans reach their genetic potential.
Factors such as health and nutrition have a huge impact on whether this happens.
When children from poorer families receive enough food and calories, they can grow to the height they inherit from their parents and grandparents.
Older people generally live longer and are less likely to suffer from heart problems and may also end up earning more.
But people can not continue to grow forever.
Like many other countries in Europe, the average height in the UK has risen in the last century – but there is evidence over the last 10 years that it is flattening.
Elsewhere, the largest increases in height in the last century have been in South Korean women and Iranian men.
The tallest people in the world are men born in the Netherlands (71.8 inches), while the shortest are women born in Guatemala (55.1 inches).
BBC
.
