Growth hormone [structure below] is often sold as an anti-aging hormone that will restore vitality and fitness in the elderly, but no proof has ever been given that growth hormone therapy extends life expectancy. Worse still: tests with mice that produce more growth hormone as the result of genetic modification show the opposite effect. GH-modified mice live shorter.
Professor of geriatrics Andrzej Bartke published an article on the subject in Neuroendocrinology five years ago, summarizing the evidence from studies with growth-hormone mice. The mice grow to be thirty to sixty percent bigger than ordinary mice and mature more quickly. Once adult they have less fat, but they also die more quickly. The mice in some studies lived only half as long.
The graph below shows the results of an experiment in which researchers compared the survival rate of transgenic GH-supermice [Tg] with that of normal mice.
In psychological tests young GH-mice score higher than normal mice. On the other hand, the GH-mice show more rapid mental decline once they reach old age.
GH-mice are more fertile than ordinary mice. They not only start to reproduce at a younger age, but the females bear more young in each nest and become fertile again more quickly after producing a litter.
It is not clear why extra growth hormone reduces longevity. GH-mice often have an enlarged liver and are more likely to develop cancer, but that is not enough to explain this.
The reduced longevity is probably an endocrinal effect. GH-mice make more corticosteroid hormone, more IGF-1 and more insulin. Insulin and corticosteroid hormone are known to speed up the aging process. Mice that don’t react to growth hormone because they have no GH receptors live longer than normal mice.
An additional explanation is that an increased growth hormone level raises the food energy requirements. The mice don’t have enough to be able to carry out repairs, as all their energy goes into growth. There have been tests in which GH-supermice live longer if they are given extra food in the form of sugar water.
In his article, Bartke does not go so far as to say that the use of growth hormone shortens life. The animal-study data do not necessarily apply to humans. But if companies are selling growth hormone as a longevity drug, you’d expect that they’d be able to back up their claims with research. But they can’t.
“The widely published ‘anti-aging’ effects of exogenous GH concern primarily changes in body composition, lipid profiles, and various indices of the quality of life rather than biomarkers of aging”, Bartke writes in the last paragraph of his article. “There are no data on the effects of GH therapy on longevity in men.”
Can growth hormone (GH) accelerate aging? Evidence from GH-transgenic mice.
Departments of Physiology and Medicine, Southern Illinois University School of Medicine, Springfield, IL 62794-9628, USA. email@example.com
Overexpression of heterologous growth hormone (GH) in transgenic mice results in numerous phenotypic effects, including a drastically shortened life span. Early onset of pathological changes in the kidneys, glomerulosclerosis and glomerulonephritis, undoubtedly contributes to and perhaps accounts for reduced longevity of these animals. However, GH-transgenic mice exhibit various symptoms of accelerated aging, including increased astrogliosis, shortened reproductive life span, and early onset of age-related changes in cognitive function, hypothalamic neurotransmitter turnover, and plasma corticosterone levels. The hypothesis that supraphysiological levels of GH can accelerate aging derives indirect support from findings in GH-deficient and GH-resistant mutant mice in which aging is delayed and the life-span is increased and from the reciprocal relationship of body size and longevity within species.
Copyright 2003 S. Karger AG, Basel
PMID: 14583653 [PubMed – indexed for MEDLINE]