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A study of top rowers has found how a naturally-produced hormone can actually make their hearts bigger and more powerful.
Italian scientists measured the hormone IGF-1 in 38 people, half of them rowers.
The journal Clinical Endocrinology reports rowers had higher hormone levels and larger hearts, both in terms of size and ability to pump blood.
A UK researcher said IGF-1 might be abused by future athletes.
Increases in the level of IGF-1, which stands for "insulin-like growth factor" can follow increases in the level of human growth hormone, a chemical which has figured in past doping scandals.
The hormone has been linked with the body's ability to trigger muscle strengthening, but this study looks specifically at how it might affect the heart.
The researchers from the Universities of Milan and Naples, used a battery of tests and measurements to look precisely at the structure and function of the rowers' hearts.
Compared with the "control" volunteers, they had larger chambers, and thicker muscle walls.
These measurements increased in line with increases in the amount of IGF-1 in their blood sample.
The rowers also had a far lower resting heart rate compared with the others.
Dr Giovanni Vitale, who led the study, said: "Our results show both the left and right sides of the rowers' hearts are larger, and function at an enhanced capacity compared with those of controls.
"The causes of this are not completely clear - it could be due to the production of growth factors, such as IGF-1, during training."
Test hope
Professor Peter Sonksen, a professor in endocrinology from St Thomas' Hospital in London, has been asked by the World Anti-Doping Agency to investigate the possibility of a test for IGF-1 abuse in athletes.
He said that it would be difficult to detect artificially-heightened levels of the hormone.
He said: "People do have different levels of IGF-1 naturally, although elite athletes do tend to have higher levels.
"You can be born with higher levels, and then training can increase those further."
BBC NEWS | Health | Big heart secrets 'aid athletes'
Italian scientists measured the hormone IGF-1 in 38 people, half of them rowers.
The journal Clinical Endocrinology reports rowers had higher hormone levels and larger hearts, both in terms of size and ability to pump blood.
A UK researcher said IGF-1 might be abused by future athletes.
Increases in the level of IGF-1, which stands for "insulin-like growth factor" can follow increases in the level of human growth hormone, a chemical which has figured in past doping scandals.
The hormone has been linked with the body's ability to trigger muscle strengthening, but this study looks specifically at how it might affect the heart.
The researchers from the Universities of Milan and Naples, used a battery of tests and measurements to look precisely at the structure and function of the rowers' hearts.
Compared with the "control" volunteers, they had larger chambers, and thicker muscle walls.
These measurements increased in line with increases in the amount of IGF-1 in their blood sample.
The rowers also had a far lower resting heart rate compared with the others.
Dr Giovanni Vitale, who led the study, said: "Our results show both the left and right sides of the rowers' hearts are larger, and function at an enhanced capacity compared with those of controls.
"The causes of this are not completely clear - it could be due to the production of growth factors, such as IGF-1, during training."
Test hope
Professor Peter Sonksen, a professor in endocrinology from St Thomas' Hospital in London, has been asked by the World Anti-Doping Agency to investigate the possibility of a test for IGF-1 abuse in athletes.
He said that it would be difficult to detect artificially-heightened levels of the hormone.
He said: "People do have different levels of IGF-1 naturally, although elite athletes do tend to have higher levels.
"You can be born with higher levels, and then training can increase those further."
BBC NEWS | Health | Big heart secrets 'aid athletes'
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