IGF-1 Blood Test – A Monitor Of Youthfulness And Disposition To Alzheimer

LE Magazine May 2004A Comprehensive Guide to Preventive Blood Testing
By Penny BaronSomatomedin-C (insulin-like growth factor/IGF-1)
IGF-1 is the main effector of human growth hormone (HGH) activity and also affects glucose metabolism (insulin-like activity). Because it remains constant in the blood longer than HGH (which tends to fluctuate in response to various stimuli), it is a more accurate indicator of HGH deficiency, and is also more precise for monitoring HGH therapy than is testing HGH directly.

IGF-1 is critical in mediating the growth of muscle and other tissues, and normal levels steadily increase until 12-15 years of age, and then begin to decline. Up to one-third of skeletal muscle mass and strength is lost between the ages of 30 and 80.66 A study by Barton-Davis et al showed that IGF-1 overexpression in the muscle cells of mice can preserve the characteristics (morphological and functional) of the skeletal muscles of old mice such that they are equivalent to those of young adult muscles.66 Ruiz-Torres et al showed that when IGF-1 levels in older (over 70) males were similar to levels in younger males (up to 39 years), the older males do not show age-dependent decreases in serum testosterone and lean body mass, nor increases in fat body mass.67

Low levels of IGF-1 have been implicated in the development of atherosclerosis. Van den Beld et al found that high free IGF-1 concentrations appeared to be correlated with reduced risk of atherosclerosis, suggesting that IGF-1 (along with endogenous testosterone and estrone) may play a protective role in the development of atherosclerosis in aging men.68

A study by Carro et al suggests a role for IGF-1 as a neuroprotective hormone. Data show a correlation between lower levels of IGF-1 and higher levels of amyloid-B accumulation in the brains of Alzheimer’s patients. In studies of mutant mice, high amyloid-B levels are seen when serum IGF-1 levels are low. Conversely, the amyloid-B burden can be decreased by increasing levels of serum IGF-1. Investigators suggested that “circulating IGF-1 is a physiological regulator of brain amyloid levels with therapeutic potential.”69

Elevated levels of IGF-1 may be indicative of acromegaly (gigantism) and diabetic retinopathy. Although it has been suspected that high levels of IGF-1 are associated with increased risk of prostate cancer, recent data suggest that IGF-1 may be serving as a tumor marker rather than an etiologic factor for the disease.70 The IGF-1 test (decreased levels) may also be used to evaluate pituitary insufficiency and hypothalamic lesions in children (diagnosis of dwarfism and response to therapy). Low levels have also been found in patients with amyotrophic lateral sclerosis.71

A study on asymptomatic HIV-1-infected subjects tested the hypothesis that oral administration of 3 grams per day of acetyl-L-carnitine (ALCAR) could significantly affect IGF-1 levels. The researchers found that while ALCAR did not raise total IGF-1 levels, it significantly increased the levels of free IGF-1 (the bioactive component of total IGF-1) in treated patients. None of the subjects investigated reported any toxicity directly or indirectly related to ALCAR administration. Remarkably, all treated patients reported subjectively, without exception, an improved sense of well being by the second to third week of ALCAR therapy.72



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