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Hormone may
hold key to helping Elderly men live longer
Newswise — Elderly men with higher activity
of the hormone IGF-1—or insulin-growth
factor 1—appear to have greater life
expectancy and reduced cardiovascular risk,
according to a new study accepted for
publication in the Journal of Clinical
Endocrinology & Metabolism (JCEM).
IGF-1 is a hormone similar in molecular
structure to insulin. It is released from
the liver and plays an important role in
childhood growth and continues to have
anabolic effects in adults.
In this study, researchers evaluated 376
healthy elderly men between the ages of 73
and 94 years. A serum sample was taken from
each subject at the beginning of the study
and researchers were contacted about the
status of the participants over a period of
eight years.
Subjects with the lowest IGF-1 function had
a significantly higher mortality rate than
subjects with the highest IGF-1 bioactivity.
These results were especially significant in
individuals who have a high risk to die from
cardiovascular complications.
These new findings come as a result of a new
form of testing for IGF-bioactivity.
Researchers in this study used a new method,
a bioassay, to measure the function of IGF-1
in the blood. Compared to commonly used
methods to measure IGF-1, the IGF-1 bioassay
gives more information about the actual
function (bioactivity) of circulating IGF-1
in the body.
“The bioassay allowed us to more clearly see
the association between high circulating
IGF-1 bioactivity and extended survival,”
said Michael Brugts, MD, of the Erasmus
Medical Center in Rotterdam, The Netherlands
and lead author of the study.
“Interestingly, we could not find such a
relationship when IGF-1 in blood was
measured with the more commonly used
methods.”
Immunoassays, commonly used previously to
determine IGF-1 circulation levels, remove
certain proteins that interfere with
accurate measurements. Recent studies
however have found that these proteins are
important modulators of IGF-1 bioactivity.
The bioassay used in this study does not
disregard or remove this protein, thus
enabling researchers to have a more accurate
understanding of IGF-1 function.
Determination of IGF-1 function using the
bioassay opens the possibility to gather new
insights about the functions of IGF-1 in the
body, said Brugts.
Other researchers working on the study
include A.W. Van den Beld, L.J. Hofland, K.
van der Wansem, P.M. van Koetsveld, S.W.J.
Lamberts, and J.A.M.J.L. Janssen of Erasmus
Medical Center in Rotterdam, The Netherlands
and J. Frystyk of Aarhus University Hospital
in Aarhus, Denmark.
The article “Low Circulating IGF-1
Bioactivity in Elderly Men is Associated
with Increased Mortality,” will appear in
the June issue of JCEM, a publication of The
Endocrine Society.
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