Male sex hormones may have an anti-aging effect on the body by stimulating production of a naturally occurring enzyme that reverses aging at the cellular level, according to a new study by Brazilian and U.S. researchers.

The research, published in The New England Journal of Medicine, suggests it may be possible to artificially stimulate production of the enzyme — telomerase, which scientists say is closest of all known substances to being a "cellular elixir of youth."

In tests of patients with genetic diseases associated with mutations in the gene that codes for telomerase, such as aplastic anemia and pulmonary fibrosis, the researchers were able to combat the damage caused by telomerase deficiency.

"One of the processes associated with aging is progressive shortening of telomeres, DNA-protecting structures at the ends of chromosomes, like the plastic tips on shoelaces," said Rodrigo Calado, a professor at the University of São Paulo's Ribeirão Preto Medical School who helped lead the research with colleagues at the National Institutes of Health.

"Each time a cell divides, its telomeres get shorter. Eventually, the cell can't replicate anymore and dies or becomes senescent. However, telomerase can keep the length of telomeres intact, even after cell division."

In 2009, Calado and collaborators published an article in the journal Blood showing that androgens, which are converted into female estrogens in humans, can be used to stimulate telomeres lengthening in cells.

For the new study, the researchers treated 27 patients with aplastic anemia — due to telomerase gene mutations — with the steroid danazol, a synthetic male hormone, for two years. The results showed the treatment increased telomeres length substantially.

The researchers are now testing the approach using nandrolone, an injectable male hormone.
Although the results of the study suggest that drugs can be used to reverse one of the biological drivers of aging, it is not yet clear whether the benefits of treatment would surpass the risks in healthy people, the scientists noted.

But some people, such as patients undergoing chemotherapy or radiotherapy, may benefit from drugs that stimulate telomerase in the future.