Human growth hormone is no ‘fountain of youth’

Human growth hormone (HGH) may not be the 'fountain of youth', according to a new study.

Researchers at the Johns Hopkins University School of Medicine have found that people, who are deficient in human growth hormone (HGH) due to a genetic mutation, live just as long as people who make normal amounts of the hormone.

"Without HGH, these people still live long, healthy lives, and our results don't seem to support the notion that lack of HGH slows or accelerates the ageing process," said Dr Roberto Salvatori.

For the study, the researchers, worked with an unusual population of dwarves residing in Itabaianinha county, a rural area in the Northeastern Brazilian state of Sergipe.

Led by Salvatori, the researchers sought to sort out conflicting results of previous studies on the effects of HGH on human ageng.

Some studies have suggested that mice whose bodies don't efficiently produce or process the mouse equivalent to HGH have an extended lifespan.

HGH has been widely touted — especially on Internet sites — as an anti-ageing marvel.

In an attempt to resolve the research discrepancies about HGH's anti-ageing value, the researchers studied 65 of the Brazilian dwarves.

Each member of this group has two mutant copies of a gene responsible for releasing HGH, leading to a severe congenital HGH deficiency.

All of the study subjects have unmistakable characteristics of the deficiency – very short stature, childlike facial appearance, and high-pitched voices.

After genetic tests confirmed the presence of the mutation, the researchers collected birth dates and, for those deceased, death dates for the dwarves and their 128 unaffected siblings among 34 families.

They compared these lifespans with each other, as well as with the death rate in the general local population.

The researchers found that those deficient in HGH lived just as long as their unaffected siblings.

Compared to the general population, those deficient in HGH had a slightly shorter lifespan, based solely on higher death rates in five females under age 20.

When this sub-group was excluded from the analysis, average lifespan among the dwarves and the general population was identical.

While the researchers are not sure why this sub-group had a shorter lifespan, but speculate that lower growth hormone levels may affect the immune system's ability to fight off sometimes deadly infections.

Of the five, four were known to have died from diarrhoeal disease, Salvatori explains.

However, why this factor affected only females is unknown.

Salvatori said that the findings suggest that levels of HGH don't affect lifespan positively or negatively.

The study has been published in the latest issue of the Journal of Clinical Endocrinology and Metabolism.