Key Takeaways

  • The thymus (an essential organ of the immune system) withers away with age. This is called ”thymic involution”
  • Thymic involution gradually leads to the collapse of a person’s T-cell potential, resulting in a drastic increase in the incidence of cancer, autoimmune disorders, atherosclerosis, systemic inflammation, and mortality in general
  • Growth hormone injections restore thymus structure and improve its function
  • These changes are accompanied by a reversal of epigenetic aging, leading to a 2-year boost in life expectancy

Actions to Consider

  • In this study, scientists used growth hormone injections to restore thymus and immunity. To enhance your own production and release of this hormone, exercise regularly and sleep enough every night. Studies indicate that these two activities have the strongest impact on growth hormone, with about 75% of the compound being released during sleep!
  • Don’t forget to support your immune system in other ways too. Adopting a healthy diet and meditating regularly are two effective strategies

Growth hormone may restore thymus function in the elderly

Immunity is an extremely important part of health and aging.

As immunity decreases with age, people become more susceptible to a wide range of life-threatening diseases, including cancer and autoimmune conditions.

There is some evidence that growth hormone could help to restore thymus function, improve immunity, and thus enhance both healthspan and longevity in the elderly.

What is this study about?

Published in September 2019 in the Aging Cell open-access online journal, this study looked if using recombinant human growth hormone (rhGH) injections would regenerate the thymus, an important organ of the immune system.

In theory, finding a way to restore the thymus in elderly adults could significantly improve their immunity, healthspan, and maybe even lifespan.

But why does immunity get worse with age in the first place?

Age-related changes in immunity

One major factor of age-related immunity decline is the thymic involution, which is a gradual withering of the thymus and its replacement with fatty tissue. The thymus plays an essential part in the differentiation of immune T-cells—and gives them the ”T” in their name.

At the age of about 63 years, thymic involution eventually results in a collapse of a person’s T-cell potential, leading to a drastic age-associated increase in the incidence of diseases like cancer, autoimmune conditions, atherosclerosis, systemic inflammation, and mortality in general.

So, how can we improve the function of the thymus?

Growth hormone to the rescue!

In this study, a group of healthy men aged 51 to 65 years received a course of recombinant human growth hormone injections (rhGH). At the same time, they were prescribed dehydroepiandrosterone (DHEA) and metformin to suppress the diabetogenic effects of rhGH.

The goal was to stimulate thymus growth and improve the immune system’s function through the action of rhGH. Here are the changes that were seen as a result:

  • Increase in thymus volume and decrease in thymus fatty tissue
  • Improvement in immune cell types, populations, and ratios
  • A significant reversal in epigenetic age and a boost in life expectancy

Specifically, based on an analysis of the GrimAge epigenetic clock, the participants gained about 2 years of life expectancy after 12 months of treatment.

What is an epigenetic clock?

Epigenetic clocks are biochemical methods of measuring age based on a person’s DNA methylation levels. 

DNA methylation is a process during which methyl groups bind to DNA molecules. These methyl groups change the activity of the sequence they bind to without modifying its core structure. So, for example, if a gene in the DNA is methylated, its transcription (decoding and action) may be suppressed. If this gene encodes a certain enzyme, this could lead to a deficit in the said enzyme.

All in all, this is a natural process through which the body regulates the genes that are expressed (active) at any given moment. Some DNA fragments are methylated, others are demethylated, and this is an ongoing process.

Since a person’s overall level of DNA methylation generally decreases with age, DNA methylation can be used to estimate one’s age more accurately than a real clock. Essentially, it’s a way of telling one’s ”epigenetic” age, which can be both younger and older than that person’s chronological age.

For example, some lifestyle, environment, and health factors can either increase or decrease DNA methylation, shifting the epigenetic clock in a certain direction. That’s why DNA methylation is often used as a predictor of life expectancy.


Both thymus function and general immunity are essential for health and longevity.

Although we can’t just go out and buy some growth hormone injections to duplicate the results of this study, it’s good to know that modern science is finding new approaches to reverse aging at the genetic level.

Who knows, maybe in a few years from now we’ll all have a robust immune system that’s not subjected to age-related changes?

Link to the study:


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