Growth Hormones (GH) and Insulin-like Growth Factors (IGF) are well known for promoting body growth in mammals. Recent studies have unraveled some new evidence showing that these hormones may also affect metabolism and lifespan.
In July 2000, Karen Coschigano and John Kopchick, two researchers at the University of Ohio, in “Assessment of growth parameters and life span of GHR/BP gene-disrupted mice” (Endocrinology 141: 2608-2613, 2000), noticed that mice in which GH receptor is absent are smaller, have a reduced body weight and surprisingly, seem to live longer than normal mice.
IGF Receptor in Brain and Lifespan
In 2003, Martin Holzenberger and collaborators, from the Hospital of Saint Antoine (Paris, France), determined that the average lifespan of mice with fewer IGF receptors than the control group was longer, similar to the longer average lifespan of the mice with absent GH receptors in the study by Karen Coschigano. Holzenberger et al. published their findings in an article, entitled “IGF-1 receptor regulates lifespan and resistance to oxidative stress in mice” in the prestigious scientific journal Nature (Vol. 421: 182-187, 2003).
Mice with Altered Brain having No IGF-1 Receptor Live Older
In another study entitled “Brain IGF-1 Receptors Control Mammalian Growth and Lifespan through a Neuroendocrine Mechanism” which was published on October 28th, 2008 in the journal PLoS Biology (PLoS Biology, 6, 10, 2144-53, 2008), the French team of Holzenberger et al. reported that genetically altered mice, where the IGF receptor is absent only in the brain but still present in other peripheral body tissue, also had an extended mean lifespan and decreased production of GH hormone.
This finding was very interesting in itself in that it showed that it is the IGF receptor in the brain, and not in other body tissue, that sets the pattern for growth and lifespan of mice. The study also raised the interesting question that environmental or psychological factors that affect production of GH and IGF by the brain may also affect lifespan of people.
The Effect of IGF on Aging Can Be Extended to Humans
These recent studies have confirmed that having a continuously low concentration of IGF in the brain and low GH in the body may very well postpone age-related mortality. Indeed, genetic mutations inactivating the IGF receptor have been found in centenarians (PNAS, 105: 3438-3442, 2008).
This result is even more significant in view of the fact that growth hormones are often prescribed to elderly people, ironically, in an attempt to compensate for the effects of aging.
However never forget that happy people live longer.
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