Rejuvenate with growth hormone? Thank you, no need!
According to the results of a study conducted by scientists at the Johns Hopkins University Medical School (Baltimore, Maryland) under the guidance of Associate Professor Roberto Salvatori, people whose bodies practically do not produce growth hormone due to a genetic mutation live as long as people with normal levels of the hormone.
This refutes the hypothesis expressed by some experts, according to which human growth hormone is a kind of "source of youth". Unfortunately, these data are unlikely to reduce the number of clinics, doctors and dealers of dubious drugs offering to rejuvenate with injections of somatotropic hormone – despite the fact that, according to the opinion generally accepted in official medicine, this benefits as much as a placebo, and the likelihood of cancer may increase.
The results of a number of studies have shown that mice whose bodies do not produce the mouse analogue of growth hormone efficiently enough live longer than normal animals. At the same time, according to other authors, a decrease in the level of growth hormone in the human body as a result of surgical or radiation damage to the pituitary gland increases the risk of developing cardiovascular diseases, which, in turn, contributes to a decrease in life expectancy. However, in such patients, there is also a decrease in the production of other pituitary hormones, which may affect the reliability of the conclusions made.
In recent years, the situation has become even more complicated by the appearance (especially often on the Internet) of a large number of advertisements containing growth hormone dietary supplements, presented to the public as a "source of youth". As a rule, such statements are based on observations according to which (but only in people with growth hormone deficiency!) compensating for its deficiency improves physical condition and reduces the severity of some signs of aging, such as thinning of the skin and a decrease in muscle mass.
In order to obtain reliable data on this issue, the authors examined 65 representatives of a unique population of dwarfs living in the municipality of Itabayaninha, part of the northeastern Brazilian state of Sergipe. In this area, midgets are born 25 times more often than on average in sunny Brazil – 80 people per 32 thousand inhabitants.
On one of half a dozen pictures for the article “Ah não!” published a year ago in the Brazilian magazine Revista Trip –
a group of Itabayaninya residents (110-135 cm) and the author of the text, a journalist Arthur Verissimo (185 cm).
Each individual of the examined group was a carrier of two mutant copies of the gene responsible for the release of growth hormone, which is the cause of severe congenital deficiency of this hormone. All the study participants had obvious signs of pituitary nanism (this disease was named after the Greek word nános – dwarf – long before the term "nanotechnology" appeared): very low height, childish facial features and a high voice.
After the results of genetic testing confirmed the presence of the mutation in the subjects, scientists collected data on the dates of birth and death of dwarfs and their 128 normal brothers and sisters, who are representatives of 34 families. After that, they conducted a comparative analysis of the life expectancy of dwarfs and their siblings with normal growth, and also compared the mortality rate in the dwarf population with the average mortality rate of the local population.
The results of statistical analysis showed that the life expectancy of dwarfs does not differ from the life expectancy of their brothers and sisters of normal growth. Although the life expectancy of dwarfs was slightly less than the average for the population of this region, this difference disappeared after the exclusion from the analysis of five women who died before they reached the age of 20.
Four out of five women in this subgroup died as a result of digestive problems. Researchers suggest that this may be due to a decrease in the effectiveness of the immune system associated with growth hormone deficiency. However, it is not known why this pattern applies only to women.
To study the possible impact on life expectancy of having only one copy of the mutant gene, the authors recruited local volunteers who came to the polling station on election day (voting is mandatory in Brazil). One copy of the mutant gene does not affect human growth, so to identify it, all volunteers submitted saliva samples for genetic testing. The number of young (20-40 years old) and elderly (60-80 years old) people heterozygous for the mutant copy of the gene turned out to be almost identical. This indicates that carrying one copy of the mutant gene also has no effect on life expectancy.
According to Salvatori, in general, the results described in the article "Longevity in Untreated Genital Growth Hormone Deficiency Due to a Homozygous Mutation in the GHRH Receptor Gene", published in the preliminary on-line version of the journal of Clinical Endocrinology and Metabolism, indicate that the level of growth hormone has neither a positive nor negative impact on human life expectancy.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on EurekAlert: Human growth hormone: Not a life extender after all?02.02.2010