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Biomarkers

IGF-1

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Insulin-like growth factor 1 (IGF-1) is produced mainly in the liver under growth hormone stimulation and mediates many anabolic GH effects on muscle, bone, and other tissues. As a biomarker it serves as a stable surrogate for GH activity and reflects nutritional status and protein intake. Higher levels in adulthood are linked to greater cancer risk; very low levels are observationally associated with frailty and reduced lean mass, though this association may partly reflect underlying disease or malnutrition rather than a direct causal longevity detriment. The net relationship between IGF-1 and longevity in humans is complex and not simply U-shaped.

Sources

  1. Key TJ, Appleby PN, Reeves GK, Roddam AW. (2010). Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies. *Lancet Oncology*doi:10.1016/S1470-2045(10)70095-4
  2. Burgers AMG, Biermasz NR, Schoones JW, Pereira AM, Renehan AG, Zwahlen M, et al.. (2011). Meta-analysis and dose-response metaregression: circulating insulin-like growth factor I (IGF-I) and mortality. *Journal of Clinical Endocrinology & Metabolism*doi:10.1210/jc.2011-1377
  3. Milman S, Atzmon G, Huffman DM, Wan J, Crandall JP, Cohen P, et al.. (2014). Low insulin-like growth factor-1 level predicts survival in humans with exceptional longevity. *Aging Cell*doi:10.1111/acel.12213