December 22, 2002
Are Replacement Hormones A Fountain Of Youth?

Gina Kolata has an article in the New York Times about the growing popularity of the use of hormones to try to roll back some of the effects of aging. Testosterone and human growth hormone (HGH) are used for men and women. Plus, estrogen and progesterone are used by women. Some use DHEA, thyroid or other hormones as well. This has intensified the debate about whether these hormones provide a net benefit.

Until recently, most scientists considered anti-aging treatments to be little more than snake oil, provided by hucksters. Now, few doubt that growth hormone and testosterone can reshape aging bodies, potentially making them more youthful.

But whether they counteract aging is unknown. And their long-term risks are ill defined. So medical experts ask whether it is right to regard aging as a disease, as fierce as a malignant cancer, to be fought with any and all means, tested or not.

First of all, yes, aging really should be fought by any means that really works. There is nothing beneficial to the individual about physical aging. An older body does not function as well as it did when it was younger. The mind doesn't function as well either. Learning is more difficult, the ability to do complex problem solving is diminished, old memories are harder to recall, and assorted brain disorders such as depression, Alzheimer's Disease, Parkinson's, and dementia are more common, . Various cells can no longer do their jobs at all and in some cases even whole organs can no longer carry out their functions. The body has a reduced ability to handle environmental changes, infections, stresses and trauma. The aged body makes life harder and less pleasureable for the person whose body has aged and for those whose jobs it is to help the aging and for those who care about and give care to aging family members and friends. The body is at greater risk of all manners of illness and death. What reason is there to be complacent in the face of all that if we can possibly do anything about it?

People who are taking testosterone and HGH are doing so because they feel immediate benefits such as better muscle tone, less fat, more stamina, perceived greater ability to concentrate, and other benefits that can be directly experienced in the short term. However, these benefits do not provide any clue as to whether replacement hormones will shorten or lengthen life expectancy. There's reason for skepticism from an evolutionary perspective: it would not have been that hard for evolution to select for an aging body to retain its ability to make hormones at the same level as the body made them in its youth. The fact that it doesn't may be because it was harmful to do so. Some hormones are known to boost the risk of some types of cancers. Also, a metabolism sped up by hormones may be akin to an engine that is operated at higher RPMs. Parts of it may wear out faster if they are being stimulated by higher hormone levels.

Another reason to be skeptical of hormone therapies is that they do cause side-effects in the short term. Most worryingly some people develop insulin resistance while on hormone therapy. The resistance usually goes away once the therapy is stopped and not all people who take hormones to feel rejuvenated suffer this side effect. Still, it is possible that a period of time spent on hormone therapy will increase the chance of developing insulin resistance (aka type II diabetes) later on.

Another reason to be skeptical of the benefits of hormones as an anti-aging therapy is that scientists have tried large numbers of experiments on animals to try to find ways to increase life expectancy. Many combinations of hormones have been tried. The only consistently successful method to increase average and max life expectancy in wild type (ie not special in-bred lab strains) found to date is calorie restriction. Hormones do not increase animal life expectancy and more often than not actually decrease it.

Is the lack of known data on the long term effects of hormone therapies an argument against taking them? The answer depends on your own personal values. Some people (I know one such person) are taking hormones chiefly for the short term benefits. They know they are taking a risk. They want a more vigorous life and a greater feeling of healthiness in their 40s, 50s, and 60s even if there is a chance of decreased life expectancy as a result. For someone such as myself who thinks that people should be able to do with their bodies as they please as long as they do not create costs for others (and someone who dies sooner is probably decreasing their net burden in terms of total government benefits that they receive in retirement) its hard to argue why this choice should not be allowed. As Blondie put it: "Die young, stay pretty, live fast because it won't last."

Having said all this, it is still possible that some combination of hormones could increase life expectancy. The problem is that there are probably many more combinations that are harmful than are beneficial and we just don't have any idea what combination might be beneficial. To know that ideal hormone regimen might well require knowledge of an individual's genetic variations and the condition of the various organs in the individual's body. It is possible that the only way to improve longer term health with hormones would involve the implantation of a genetically engineered or silicon-based hormone dispenser organ that could deliver hormones with a greater precision than what is possible thru the use of pills or shots. Such an implant could take into account the constantly changing internal condition of the body to adjust the levels of hormones to a more optimized level. This sort of capability still lies somewhere in the future. But it seems plausible that some day it will be possible to develop a better endocrine regulatory system than the one that we are all born with naturally.

The problem today is that we lack the knowledge to know whether or how we could tweak the endocrine system of humans to extend life. Even if we knew how to design and build an incredibly sophisticated device for monitoring metabolism in real time to adjust hormone levels of aging people we still wouldn't know what to tell the device to do. Hormone levels change as we age. Why? Here are some possibilities for why hormone levels change as we age:

  • The change in hormone levels of aging bodies could be the result of natural selection aimed at maximizing life expectancy of an aging body.
  • But the changes might instead be a result of a decay in the ability of the aging endocrine systen to optimally regulate hormone levels.
  • The changes might be because natural selection just did not select strongly enough for an optimal regulation of hormones in an aging body (as an analogy think of a computer program that hasn't been well enough tested, debugged and optimized under some operating condition).

We do not know which one or combination of these possibilities is correct. Even if we did we wouldn't then immediately know what to do about it. People who are taking replacement hormones are therefore engaging in a massive experiment in hopes that anything that provides an immediate benefit will provide a longer term benefit as well.

Share |      Randall Parker, 2002 December 22 03:46 PM  Aging Drugs


Comments
RB said at December 23, 2002 2:57 PM:

It is dangerously close to the teleological to posit what "natural selection" has chosen for the aging human. Any physiologic change that takes place after the age of reproduction in a human cannot be said to have been selected for, specifically. Only to the extent that an aging pattern is strongly associated with a trait or set of traits lending superior procreative power to the human in its younger years, could an aging pattern be said to have been "selected."

Randall Parker said at December 23, 2002 3:34 PM:

Yes, physiological changes that happen after the age of reproduction are selected for. Once a woman ceases to give birth her ability to survive and care for her offspring (and even her offspring's offspring) will affect the ability of the offspring to survive. If humans were a species that laid eggs and then left them to fend for themselves then your argument would have merit as there would be no selective pressure on post-reproduction viability. But of course we do care for our offspring for many years and even grandparents help.

The help of grandparents has been shown to make differences in infant mortality rates in recent studies with the maternal grandmother's presence being of greatest benefit (and not coincidentally its the maternal grandmother who can be most certain that the grandchild is descended from her).

Lonnie Torrence said at November 15, 2005 10:51 AM:

The aging process "can" be reversed through the use of hormones!...BUT...there's another element to be considered in order for it to work.

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