Insight 17 – Despite considerable evidence to the contrary, human growth hormone maintains a reputation as a valid anti-aging therapy.  There exists a wealth of over-the-counter supplements claiming to elevate growth hormone levels and restore youthful vigor.  Unfortunately, claims of rejuvenation are exaggerated and associated adverse effects are played down.  This blog will discuss these issues and define alternative ways to stay healthy without human growth hormone supplements. 

Introduction

Growth hormone is one of many hormones produced by the pituitary gland, a small endocrine organ located at the base of the brain.  As aptly named, growth hormone plays a major role in the growth of an individual from birth to puberty and young adulthood.  However, growth hormone cannot take all the credit for influencing our growth.  It stimulates production of a liver hormone, insulin growth factor-1 (IGF-1), and the two partner together to exert biological influence. 

Changes in Growth Hormone with Age

Blood levels of growth hormone peak at puberty and decline about 80% by age 55 (as does IGF-1).  Along a similar timeline, muscle and bone mass peak in young adulthood and slowly decline with age roughly correlating with a fall in circulating growth hormone.  Since growth hormone and IGF-1 are significant effectors of muscle and bone health and since their levels fall with age, scientists reasoned that restoration of growth hormone to youthful levels (by infusion or injection) would reverse age changes in muscles and bones.  Hence, growth hormone should provide the desired rejuvenation.

Can Growth Hormone Rejuvenate the Aging Body?

Using the newly available synthetic growth hormone, a small study of 21 men (61-81 years of age) measured lean body mass (roughly muscle mass), fat mass, skin thickness and bone density before and after 6 months of daily injection of growth hormone (Rudman et al., 1990).  In 12 elderly men receiving growth hormone, muscle mass (8.8%)  and  bone density (1.6 %) increased, skin thickness increased (7.1%) and fat mass decreased (14.4%) compared to controls.  In 1990, these remarkable and significant findings supported the concept that growth hormone had rejuvenating powers.

The Negative Side of Growth Hormone

Sadly, this study and related hype raised appropriate skepticism.  Firstly, the study by Rudman et al., (1990) was too small for fundamental generalizations.  Additionally, treatment-associated negative effects such as an elevation in systolic blood pressure and fasting glucose levels in those receiving growth hormone, took a back seat.  Secondly, a review of 18 clinical trials (Liu et al., 2007) with growth hormone injections in men for up to 27 weeks, confirmed the earlier findings but emphasized that the extent of changes in body composition was very modest.  

Importantly, the small positive changes were outweighed by serious adverse effects. These adverse effects included:  a)  soft tissue swelling (edema); b)  joint stiffness (arthralgias); c) carpal tunnel syndrome (nerve compression due to fluid retention causing hand and finger pain); d)  enlargement of male breasts (gynecomastia) and e)  impaired fasting glucose (risk factor for diabetes mellitus).

Thirdly, despite the increase in muscle mass, there was no comparable increase in muscle strength.  This is exceedingly important because age-related loss of muscle strength (not muscle mass) leads to loss of physical independence.  Therefore, despite youthful levels of growth hormone, the beneficial effects in the elderly are too minor to warrant multiple serious adverse effects with no gain in muscle strength. 

Can Growth Hormone Accelerate Aging?

There is a wealth of evidence gathered from animal studies that a deficiency of growth hormone, whether artificial (genetic manipulation) or natural (hereditary) slows many aspects of aging and increases longevity.  On the one hand, growth hormone deficient animals exhibit small size, delayed puberty and reduced fertility.  On the other hand, these animals live longer than controls with normal growth hormone levels.  This is because many anti-aging activities such as increased resistance to stress and decline in pro-inflammatory mediators are enhanced when growth hormone is scarce.  Together these activities and many more, support a longer lifespan with lower levels of growth hormone.   

Genetic disorders of growth hormone deficiency in humans exhibit similar changes.  These individuals exhibit a resistance to major diseases and although they do not have exceptional longevity, it appears that they enjoy a longer health span.  Taken together these findings suggest that growth hormone therapy for the healthy elderly has a significant potential to accelerate age changes.

An Alternative Approach Without Growth Hormone

As noted above, growth hormone use does not make muscles stronger.  Therefore, as discussed in (Insight  3, Progressive Resistance Exercise) a proven way to increase muscle strength is engagement in a serious program of resistance exercise, e.g. hand held weights or machines.  A program of progressive resistance exercises of increasing difficulty at home or in the gym will maintain muscle strength.  Optimal muscle strength ensures continued independence. Specifically, this is independence to carry out daily activities e.g. shopping, walking, housework. This leads to a better quality of life.  Additionally, progressive resistance exercise preserves balance and prevents falls

The Marketing of Growth Hormone Supplements

Growth hormone medications exist in many forms, all approved by the FDA.  Physicians prescribe them to treat well-defined endocrine deficiencies, affecting patients of all ages.  In contrast, the healthy elderly rely on advertisements of growth hormone supplements.  Websites claim that supplements, called secretagogues, boost blood levels of growth hormone.  Secretagogues are mixtures of select amino acids. 

Thus far, only one company tested their proprietary secretagogue mixture in human trials (2 clinical trials; 16 volunteers each).  Growth hormone levels rose significantly after a single oral dose of their secretagogue.  This information is worthwhile but it is extremely limited. 

Firstly, consider there are no clinical data at all for the many growth hormone secretagogues on the market.  Secondly, the two small trials mentioned above require confirmation by a larger number of volunteers, preferably with different doses and longer duration of use (not just 2 hours).  Thirdly, there are no data on the assumed positive effects of these supplements on energy output, muscle repair, and anti-aging potential.  Furthermore, there are no data on the negative adverse effects of these supplements.  

As stated above and reviewed by others (Bartke et al., 2021;Colon et al., 2019), the adverse effects of clinically tested growth hormone injections in the elderly outweigh the small effects on muscle, bone and fat mass.  Until evidence exists to the contrary, secretagogues that raise levels of growth hormone are expected to exhibit the same results.  Until more thorough trials are done, the best way to improve muscle mass and strength and decrease fat mass is with resistance and aerobic exercises.

Summary

Growth hormone fails as a hormone of rejuvenation.  In fact, extensive data in animals and some observations in humans suggest that growth hormone accelerates aging.  Clearly, for the healthy elderly, the multiple severe risks of growth hormone use far outweigh the small changes in muscle, bone and fat mass.  There is a safer way to build both muscle mass and strength.  It is an engagement in a progressive resistance exercise program either at home or at the gym.