IGF-1 LR3 Biochemistry and Interactions

IGF-1 LR3 is an analogue of IGF-1. The molecule is longer than IGF-1 by 13 amino acids and has a single amino acid substitution at the 3 position (arginine in for glutamine). These changes make IGF-1 LR3 more potent and provide it with a longer half-life (30 hours versus 15) compared to endogenous IGF-1. IGF-1 LR3 biochemistry is complicated by the sheer number of interactions that occur between IGF-1 LR3 and other endogenous hormones.

IGF-1 LR3 and Human Growth Hormone

Human growth hormone (hGH or HGH) is released from the anterior pituitary gland in the brain. One of its main functions is to stimulate the production and release of IGF-1 in the liver. IGF-1 then goes on to promote cell growth and division. HGH has a number of effects that IGF-1 does not have. For instance, HGH stimulates the immune system, affects thyroid hormone levels, and causes hypertrophy (growth in size) of a number of cells.

Exogenously administered IGF-1 LR3 has been shown, in animal testing, to produce some of the effects that growth hormone produces. For instance, IGF-1 LR3 can stimulate muscle growth and increase fat metabolism. It does not, however, affect the immune system or thyroid hormone levels. IGF-1 LR3 will cause hyperplasia (cell division) rather than hypertrophy. IFG-1 levels to not appear to affect HGH secretion or regulation. IGF-1 LR3 has been shown to have little to no effect on growth hormone levels in animal testing.
IGF-1 LR3 and Insulin

IGF-1 and its analogues bind readily to the insulin receptor. At relatively low doses, exogenously administered IFG-1 LR3 appears to lower blood glucose levels directly while lowering blood insulin levels both directly and indirectly. As a result, IGF-1 LR3 appears to decrease the risk of developing insulin resistance and thus diabetes. Studies in diabetic animals suggest that, when IGF-1 LR3 is administered in physiologic doses, less insulin can be administered (roughly 10% less) with excellent blood sugar control. At higher doses, IGF-1 LR3 increases the risk of hypoglycemia (abnormally low blood sugar) by about ten-fold.
IGF-1 LR3 and Testosterone

There isn’t a great deal of research into the effects of IGF-1 LR3 administration and testosterone levels. Limited evidence suggests that the two hormones are synergistic and that IGF-1 LR3 can even reverse testicular atrophy due to low levels of testosterone. This makes sense given that research into the effects of testosterone on IGF-1 levels in neonatal foreskin fibroblasts has found that testosterone increases IGF-1 levels1. Higher IGF-1 levels may increase male sexual function, a finding that has led to the investigation of IGF-1 LR3 to treat erectile dysfunction and reduced fertility in men.

IGF-1 LR3 and Glucocorticoids

Glucocorticoids are secreted from the adrenal glands and play a prominent role in controlling inflammation throughout the body. New research suggests that IGF-1 is an integral part of at least one aspect of the glucocorticoid signaling pathway. Glucocorticoids, which have long been associated with muscle wasting and adipose tissue gain, appear to increase the resistance of certain cells to the effects of IGF-12 . Understanding this interaction may allow physicians to prescribe IGF-1 analogues, like IGF-1 LR3, to counteract some of the negative effects of glucocorticoids. This could potentially allow individuals to take much higher doses of glucocorticoid or even to take the drug for longer durations to time to achieve lasting relief from pain, autoimmune diseases, or general inflammation.


1. Ashton, W. S., Degnan, B. M., Daniel, A. & Francis, G. L. Testosterone increases insulin-like growth factor-1 and insulin-like growth factor-binding protein. Ann. Clin. Lab. Sci.25, 381-388 (1995).

2. Hanaoka, B. Y., Peterson, C. A., Horbinski, C. & Crofford, L. J. Implications of glucocorticoid therapy in idiopathic inflammatory myopathies. Nat. Rev. Rheumatol.8, 448-457 (2012).

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