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PEOPLE taking growth hormone supplements may actually be shortening their
lives, scientists warn after a study on genetically engineered mice.

Levels of growth hormone drop as we get older, and some physicians have shown
that supplements can reverse muscle wasting in old age. And some children,
deemed a bit on the short side by parents or doctors, receive injections of
growth hormone even if they don鈥檛 have a growth hormone deficiency. In the past
the only drawback was seen to be the expense of achieving an extra 5 centimetres
in height on average, but alarm bells started to ring when a study in the US
showed that mice incapable of responding to growth hormone live longer than
normal mice.

Researchers know that dwarf mice with low levels of growth hormone are
unusually long-lived. But these mice lack other hormones too, making it
impossible to tell which hormone deficiency makes them live longer. So Karen
Coschigano of Ohio University in Athens and her colleagues genetically
engineered mice to lack the growth hormone receptor. Although these mice
produced normal levels of growth hormone, they were unable to respond to it.

The mice were less fertile and had weaker bones than normal mice, and were
about half the normal size. But surprisingly, they also lived nearly a year
longer. Coschigano believes her study suggests that people should use caution
when taking growth hormone supplements. 鈥淭here鈥檚 negative and positive effects
of growth hormone,鈥� she says.