Researchers found that treatment with growth hormone not only boosted growth in children, but also improved their conduct and relations with other people.

Lead researcher Dr Brian Stabler, professor of psychiatry and pediatrics at the University of North Carolina, said: "We believe this work demonstrates that all very short children need to be evaluated thoroughly by psychologists as well as by paediatricians and endocrinologists."

Emotional and psychological problems

Growth hormone can boost height and improve behaviour

A sample of 195 short US children, aged between five and 16, were tested for intelligence, academic achievement, social skills and behaviour problems before starting growth hormone therapy.

They were examined again over a three-year period after starting treatment.

Scientists initially found the children suffered a significant level of emotional and psychological problems including anxiety, depression and attention deficit.

Despite achieving lower grades at school, the children had near average IQs, and neither IQ nor achievement test scores changed with treatment.

Hormone secretion

However, after hormone therapy behaviour problems improved. The children were less anxious, attention improved and they were more open.

Dr Stabler said: "There are several possible explanations for the improvements.

"One is that growth hormone therapy boosts brain chemicals and neurotransmitters that did not work as well as they would have if hormone secretion had been normal."

Behaviour problems in short children improved quickly with six months of hormone replacement therapy, Dr Stabler said, but that could not be due to growth alone as height increased slowly.

Dr Brian Jacobs, a child psychiatrist at The Maudsley Hospital in London said more research was needed before the link between growth hormone and behaviour was fully established.