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Biomarkers

IGF-1

Insulin-like growth factor 1 (IGF-1) is made mainly in your liver, under stimulation from growth hormone (GH). It carries out many of GH's anabolic effects on muscle, bone, and other tissues. As a biomarker, IGF-1 is a stable stand-in for GH activity, and it reflects your nutritional status and protein intake. Higher levels in adulthood are linked to greater cancer risk. Very low levels are observationally tied to frailty and reduced lean mass. But that link may partly reflect underlying disease or malnutrition, rather than a direct causal harm. So the net relationship between IGF-1 and human longevity is complex, and not simply U-shaped.

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